Stop having sex? Not much more to it than that. This whole 'born again virgin' thing isn't biblical, if you're getting at that. That's just a man made concept to ease the sense of guilt people have for their actions, instead of Actually confronting it.
Once you've had sex, you can't go back in time and erase it. You are forgiven by God, of course, but you need to accept that that is all that matters. People can't take their sins back and pretend they didn't do them.
It's funny how sexual sin is the only sin people want to take back, but it's also the only sin listed as 'a sin unto your own body'.
By the way, even if you are engaged that doesn't excuse having sex. Sex is meant till After marriage, not until you're sure you found the right person. The foundation of your relationship stopped being God based soon as you made that decision.
Not trying to put you down. We all make mistakes. But keep in mind there is no taking them back. I was 13 when i lost my virginity. Now i'm 40 and still regretting that decision.