Check the Program
A minor note, but one that deserves to come first. Your rolls were extremely low, but they did tend to cluster around 5 (all but two rolls within 2 of five). I think it's possible that something may be set up wrong on your roll20 character sheet.
click on the "gear" symbol on the upper right of your character sheet, then look in the upper right box. It should say "Core Die Roll" and have 1d20 written there. If it says "Core Die Roll 1d10" then that's your problem.
However, since you did roll an 18 for initiative, it's possible that you simply got extraordinarily unlucky. So with that in mind, read on:
Improving your odds/fun in combat
There are three basic ways to excel in combat.
Play to your strengths
Fit your goals to your circumstances
Improve what you need and don't have
Let's talk about how each of these applies to your character.
1. Play to your strengths
Paladins won't attack as often as Monks or (at higher levels) fighters, but when they chose to they can hit hard. As such, they aren't really built for dealing with multiple enemies, but paladins are excellent at dueling single strong foes and dealing "nova" damage (large amounts of damage that can only be done a few times).
In the combat above, it might have benefited you to focus on a single target, like the boss. Even with abysmal rolls, you'd be serving as a "tank" to your team, directing attacks away from allies of yours with lower HP or AC. And you could have benefitted from the actions of your allies as well (such as gaining advantage against the boss if an ally knocks them prone, or casts hold person on them). And you could have used your paladins' Chanel Divinity feature of their divine oath against this stronger foe, which often improves your odds of hitting an enemy (such as the Oath of Devotion's Sacred Weapon feature, which would have let you add a +2 to all your attack rolls).
Running after multiple enemies is exactly the kind of thing a paladin is bad at. You'll spend a lot of resources dashing to keep up with them, and may waste resources smiting them by doing more damage than their total hit points (thus "losing" damage that could have been dealt to a larger target). Also, very few 3rd level paladins have Area of Effect abilities or spells, so they cannot damage a large number of enemies quickly (unlike spellcasters who could use spells like shatter or spike growth to damage several enemies at once). Although there are going to be situations where you should pursue a mob (and this may well have been one of them), know that running after a group as a paladin is like running into melee range as a wizard: there are times to do it, but it's usually a sign something has gone wrong.
2. Fit your goals to your circumstances
You're a righteous paladin in shining armor, with literal wings extending from your back. You look like the angry face of justice from on high, come to earth to punish the wicked. Who in their right mind would stand against you?
Unfortunately, that's exactly what you wanted your enemies to do. You ran in front of them, hoping they'd all stop and attack you. As an aarakocra in heavy armor, you're slower than most standard enemies (walking speed of 25 feet), and you lack the movement advantages of a monk or rogue, so the best chance a minor enemy will have is to simply outrun you: to find an easier target.
If you want to chase these enemies down (which is totally understandable: they are threatening innocent people), your goal can't be to catch and defeat them all: best case scenario, that would take 6 rounds, which is quite a long time. Not to mention the fact that they are faster than you, and don't want to stop and fight if they can help it. So you need to use a tactic which will work at a distance, and use the fact that they are afraid to face you to your advantage.
For example, you could try to intimidate them into surrendering. If that's the goal, then even failed attacks could work towards your goal. If a feathered and armored creature was swinging a sword inches from my face, shouting that I must yield or die, I'd really reconsider my life choices up to this point. These enemies clearly want nothing to do with you (they keep running past you) so use that weakness as a strength. That way not only will you have a greater chance of defeating them all quickly, you'll also feel like you've contributed more to their eventual surrender even if all your rolls fail. (You describe this combat as the town guard convincing them to surrender: but if you'd been shouting at them to yield, maybe it was you who convinced them to give up). With the right goal, you can work towards success even when all your rolls fail.
I'm not saying you need to shout "surrender" in every combat: I'm saying fit your tactics and goals to your enemies and situation. If your enemies are faster than you, know that you can't swing a sword over distance but you can shout very far. If your enemies are afraid of you, convince them to surrender rather than face your blade. If your enemy is overconfident, lure them into a fight that is to their disadvantage. Any enemy psychology or feature of the terrain can be turned to your advantage.
3. Improve what you need and don't have
In this battle, you prioritized attacking enemies that were running from you. But your major tactical advantage you gave yourself was to cast Shield of Faith and increase your AC.
Increasing AC fixed a problem you didn't have: you made yourself harder to hit, but your had excellent AC already, and your enemies do little damage per strike. Besides, your opponents already showed that they would run right past you given opportunity, so standing in front of them and improving your armor didn't really help you stop them. If your goal was to chase them down, what you needed was to hit consistently so you could take down your enemies quickly and move on to the next one. This must have been especially clear after your second round of combat, where none of your strikes seemed to connect.
A spell like bless would have been more effective here, increasing the probability that you land a blow (and helping your allies at the same time). Similarly, using your Chanel Divinity might have been very helpful. If you had the Oath of Devotion (which sounds likely), and if you'd used sacred weapon and bless at the same time, you'd have added an average of 4.5 to every single attack roll you made (minimum 3) which would have likely turned four of your five attack rolls above into hits. It might have even turned your worst attack roll into a hit (2 + 5 dex and proficiency + 2 Charisma + 4 a lucky bless roll = 13, higher than a standard bandit AC).
Looking ahead, you might have noticed that mobility was an issue for you in this battle. You can fix that by swapping out your heavy Ring Mail armor for Studded Leather (same AC next level if you improve your Dex), and gain an extra 25 feet of movement every round through flying. Alternatively, since the aesthetic of your armor is important to you, could invest some money (75gp) in a mount like a riding horse (until you can cast Find Steed in two levels).
I've been told before that "the goal of war is to find a fair fight and make it unfair." If you find yourself having trouble with something (rolls to hit, mobility, whatever), look for resources that can improve those things. And you don't need to only look to your character either. Maybe your team's wizard will cast magic weapon on your sword before the fight begins, or your teams druid will cast entangle on the fleeing enemies and give you advantage on your strikes.
Sometimes, nothing will work
You were insanely unlucky in this last game. The odds of rolling below a 10 (naturally) on 5 attacks is about 1/32, and you managed to roll abysmally for another three rolls besides. This kind of bad luck will happen once in a blue moon: but it's worth acknowledging that it will happen.
This will happen sometimes, even if you pick all the right tactics and have optimized your build. Every now and again, Gimli gets stuck under a warg, or a stealthy smuggler steps on a dry twig. No matter how good you are, sometimes everything will go wrong.
If you follow the guidelines above, then hopefully these times will be few and far between, and they will not last very long. My biggest advice is "use it." Are you getting frustrated? Then so is your character. Let that rage and frustration fuel them to train even harder, to search or that next magical item, to learn that new spell which will make them more able to turn a miss into a hit, a failure into a success. Do you feel like this is ridiculous? Then laugh. Reframe the misses as comedic, and imagine how funny it would be to see the mighty paladin spout justice and hellfire, but then miss.
In the words of Maya Angelou: "you should be angry. You must not be bitter." The role of random chance in your successes or failures is more on display in a role playing game than in real life: you can always see how there are elements of the game that our out of your control. But just because some things are out of our control doesn't mean everything is. Every situation has something you can do to turn it to your advantage, some way to improve your odds. And if you do all that and still fail, let it motivate you to do even more in the future: to make your character even better. And the better you get (and the more you use tactics that work to your advantage), the more often you'll find even mediocre rolls resulting in a success.