I regret my past. I think most people do. Sometimes I try to tell him about my past so he can share in the hurt, or at least know where I'm coming from. He doesn't want to hear it - and I don't blame him. I wish I could be like that. I know the only thing that should matter is here and now, but I'm tortured. I'm hurt I'm not his one and only.
That's why this bothers you. Others are giving sound advice -- live in the present, don't dwell on the past. Only this is really hard sometimes.
For you, I'd advise jumping head first into all those past regrets. It's great you've tried to talk to him about it, but if he (understandably) doesn't want to go there, you may have to try and talk to someone else. You won't find it easy to liberate yourself from his past until you are comfortable with your own.
So talk about it with someone (even on a forum) - it'll help!
As for regrets in general, think about it this way. You either:
-Made a mistake in the past and learned from it to the point where you understand why you made it and it won't happen again, or
-Made a mistake in the past and still think the mistake is somehow part of you. As in, you'd do it again, or it makes feel you bad as a person, etc.
The reality, we all make mistakes. And we all mistakes for a reason...
if we didn't understand them and dwelled on them and brought them with us, we'd be cursing ourselves for life for peeing in our pants at the age of 4.