Sorry to hear about that. I feel that you contribute a lot greatly for others on here; and I'm sure they appreciate you. When I was your age I felt exactly the same way. I went to college but felt like I had just barely got by. I had fears for the future, thinking that I'm not going to be destined to be anything. Socially, at that time, not so great too.
As of now, I am three times your age. I have had accomplishments but I feel like not nearly as good as others around my age and younger. So many people have told me that I have done extremely well for myself. I find it hard to believe. I read a book from a professional counselor; and the writer had said that he's amazed how there are those whom had accomplished great things and they have a low opinion of themselves. I guess that's what depression can do.
For me, the greatest accomplishment was just recently when I had sold my condo unit. I received two-and-a-quarter times more than what I had originally purchased it for. And now I'm able to invest. Plus I had successfully been working at the same job that I like for 13 years. Not bad for someone that so many people told me, "you're gonna go down like a lead balloon!".