Not all hope is lost, there are several ways you can help your allies.
##By dealing non-physical damage
By dealing non-physical damage
Magic weapons aren't the only way to bypass physical resistance/immunity.
You can achieve this effect by:
- Asking your party spellcasters to cast a relevant spell (such as Dragon's Breath)
- Utilizing environment features (pushing enemies into fire etc.)
- Using consumable items (e.g. Alchemist's Fire)
##By controlling a battlefield
By controlling a battlefield
Pushing, grappling, tripping - everything you can imagine. Unless you dumped your Strength ability score, it should not be a serious problem.
##By helping your allies to land an attack
By helping your allies to land an attack
Using an action to help an ally will grant an advantage on their first attack, increasing effective DPR of your team as a whole.
##By provoking enemies to attack you/absorbing damage
By provoking enemies to attack you/absorbing damage
Essentially, by taking a tanky role, you will enable your teammates, if it isn't being effective, then I do not know what could be. Damage prevention is nearly equal to healing.
- Taking Magic Initiate and choosing Compelled Duel allows you to draw enemies' aggro just like in MMORPGs.
- Using a dodge action applies disadvantage to attacks against you and grants advantage on Dexterity saving throws.