Nah you have done nothing wrong, i think a lot of people go through this. I did.
You are in college/sixth form i take it?
I suggest going to people, whether from the same subject or you happen to have a common interest?
"If lifes passing you by, trip it up!" a quote i was given. Use it, if your being ignored then try and get involved with them.
If your shy or self-conscious i agree it is a lot harder, but not impossible. I found diving into studies (taking an extra A-level with 4months to do it!) helped, well you still get down about too much work, but distract yourself.
How about out of school? no friends from like year 11 and before that you can start talking to again?