Even Though Everyone Else Has Grown, I Still Feel Small

I used to think I was just a normal kid,  a normal smart kid if that makes sense. That means I've been in classes with many of the same kids for years. I thought it was fine to only take one or two AP/IB classes a year since I didn't want to overstress and try and have more of a social life, but when I look at the rest of my classmates I feel inferior. They're fun, outgoing people who seem to do six to eight AP/IB courses like it's nothing. They are able to volunteer, be top of the school and hang out more than I do.

School was/is the only thing I feel that I can brag or feel accomplished about. I can't do a lot of volunteering because I have to watch my little brothers constantly and there are few opportunities in my area that I can bike to (we only have one car, which either my mom and/or older brother uses daily). I can't get a part time job. I'm not exactly sure what college I'm going to go to. I don't know if the career I'm planning is what I really like or a phase. 

As for relationships, I can't say I have any close friends, not even with the people I've been friends with since elementary school. I think a part of this is due to trust issues due to my bastard ex-stepdad, but another part is that I feel boring, pathetic and dependent. I never have anything to talk about with the friends I'm with. I'm scared that if I ever talk to them about myself that I'm annoying. I always need someone's assurance that I'm doing the right thing or doing well in life. I can't invite my friends over due to my little brothers messing up the house and being a pain; many times when I have cleaned the house in anticipation for my friends, they have to cancel. I'm letting a friend drift away even though I promised that I wouldn't.I don't know what to do.

I wish that I could become stronger.