Guilt after abortion

I have my reasons for my abortion, it was the right thing to do and I know that, but I have this awful over whelming feeling of regret and my god do I wish I could go back and undo it. I haven't had sex since because of the fear of getting pregnant and having to do it again, but at the same time I want another chance, so bad.. I'm 16 so I can't just try again atm, please can anyone give me some advice?