Role-playing Games Reward Specialization
The ability to do one thing well is better than the ability to do many things poorly.
A character who can do a little bit of everything is only successful in one-on-one play, and he is only successful because there aren't other characters. In group play, characters generally assume... well... roles. Those roles differ vastly from campaign to campaign, but usually 1 character gets 1 role, and when that character's not present that method of problem-solving must be acquired by the other players in play or ignored in favor of the resources available.
It sounds like what you're doing is trying to be an action hero, and action heroes aren't the best model for characters in a role-playing game because of most role-playing games' ensemble nature. The action hero works alone, does everything himself, and wins. You can do the first two in a role-playing game, but that last will be elusive. Few games expect every character to handle every situation. Instead of trying to be the team, try to be part of the team.
Your Character's Specialty Makes Your Character Valuable
It doesn't matter what it is. In Pathfinder, you could be the guy who bargains with monsters, makes magic items, casts divination spells, sneaks around, or whatever, but you should pick something and be as good at that as you possibly can. If you're the best at something, you'll be contributing because that's what you're best at is how you solve problems.
Option 1: Talk to the Other Players
If you don't know in what you can or should specialize, talk to the other players, including the DM, and find out the campaign's themes and current group composition, and set about making the best character for the campaign that complements that group. In my last Pathfinder group, the DM said that the campaign was an fantasy urban police procedural with a few combat-heavy characters. My half-orc inquisitor who could track anything was quite valuable; although the other characters hit things harder, he made it to where we found the things we were supposed to hit more quickly.
Option 2: Play What You Want
If you know what other characters are involved, pick something they're not doing and do it. Here's the secret: It doesn't matter what it is. Unless what you've picked is straight-up inapplicable (e.g. the greater stage actor in the world... in a dungeon-crawling campaign), that becomes what you do, and your method of solving problems becomes that. When you turn yourself into a hammer, the world's a nail.
A Problem with Pathfinder
Pathfinder has more than a few character classes that are perfectly survivable and that contribute just fine at low levels but expire at higher levels. Further, Pathfinder punishes multiclassing (or, depending on one's point of view, rewards single-classing), so once a class reaches its expiration date, getting out usually means abandoning the character rather than trying to make him go. Such a character will never be as good as those who started off being good at what they do. My half-orc inquisitor made it to level 9, but he was obsolete; had the campaign continued, he would've retired, and I would've brought in a character who could contribute better alongside the alchemist, cleric, and summoner. He was becoming a burden. He had maybe two levels left. And that's okay.
Play a Full Caster!
You've played a gunslinger, magus, and monk, and all of these have expiration dates. Only one casts spells, and Pathfinder loves casters. I urge you, if you want a character who's competitive throughout his career, pick a class that eventually casts 9th-level spells. Your niche is much bigger with a full caster, and one with a varying spell selection means that if you do feel like you're not contributing today, you can contribute better tomorrow by picking a whole new suite of spells.