First of all, what he did before he was your boyfriend isn’t really up for debate. We all bring pasts to the table, and it’s likely that he did sleep with her — but he wasn’t dating you at the time, so he wasn’t cheating on you. You have to remember that.
You should not try to give him rules about who he can see and who he can’t see. If he is honest and has a good moral compass, as you described him, then he knows what’s right and wrong. What you can do is be the girlfriend he WANTS to spend his time with. If you get to a point in a relationship where you’re forbidding a guy you’re dating from talking to or spending time with another woman then you’re either not doing YOUR job of enticing him to be with you, or else you’re not well matched. Decide which it is in your case — if in fact you find this to be a real problem (and not just an imagined one).
Getting over your own past is your job. Don’t sabotage good relationships because you’ve had bad ones in the past. Use what you’ve learned (and if you don’t learn your lessons, you’ll keep getting opportunities to learn them over and over until you do!) to choose wisely.
I hope this helps. Let me know how things go — and please follow me @AskAprilcom on Twitter and on Facebook at this link: [url]http://www.facebook.com/profile.php?id=100001113133958[/url].