Before wondering what's wrong with you, you should first check to see whether everyone around you isn't just a jerk. Once you find that to be untrue, then look at yourself.

Sometimes we just find that we don't fit in quite as well as we hoped. Other times, we realized too late that we were fitting in just fine, we were just overanalyzing it. Are you sure that isn't the case? I find that those who suffer from depression or anxiety of some sort are more inclined to feel "left out" more often than people who don't.

Until you sort that out, find another club or group. Make sure it's something you enjoy doing. Hopefully you can make friends with a shared common interest.

Hope that helped! Good luck!