I was 15, and I don't regret it at all, because it gave me experience. I do regret not being more careful, though. Although I was only with one partner (at the time) I didn't make him use condoms because we were taught to abstain, so I didn't know about the other options until almost a year in! A friend of mine mentioned something about a pill that you could take daily and prevent it (who woulda thunk it?!) and that's when I talked to my doctor about different types of birth control and was put on the Depo shot.
I'm a perfect example of why abstinence only sex-education lacks the actual EDUCATION part. It didn't stop me from having sex, just made me less prepared and far less educated about how to avoid getting an STD or pregnant.