Hi Travis. =] Yeah, I'm just a slightly bit open about when it comes to older guys dating younger girls. But anyway.. It's just the fact that you're dating someone that is underage. It's not the problem that you're 2-3 years older than her, it's that she is underage, a child, that anyone 16 or over is not allow to have sex with her even if she says it from her own mouth that she wants it, of course that won't stop anyone from doing it, but if you're caught, you might be in big trouble. You can try to mend the relationship with her parents, but the fact that they went as far as to forbid the two of you to see each other, there's not much to hope for. All I could suggest you doing is to apologize to her parents for doing it and to say that she wanted it too. But I don't believe most parents would want to allow their 14-15 year old girl to continue seeing their boyfriend if they know it's to the point where they have sexual relations. I believe they would be able to put you in jail or something like that if they wanted to, so I would also suggest do not get on their bad side and if they do threaten to go to the police, you can't do anything more than that sadly.
I wish you good luck Travis.