major jealousy

I'd just really like some answers and thanks in advance to anyone interesting in responding.
Just to give you a little background, my fiance and I started out badly. He was married when we got together, not happily, and I was just plain old not happy. Before meeting him, this jealousy issue wasn't a problem. Now I think because he cheated on his wife with me, he'll do it again. It was a horrible thing for us to do and I regret it. I wasn't strong enough to wait.
Here's the thing: whenever we meet new people, I am instantly jealous of the woman. I always think my fiance is attracted to them. Well now we have one living next door to us. And she has a gorgeous friend. I always wonder if her friend will be over and I never get any peace. I'm either worrying about her being there, or worrying that she might be there soon!
Anyway, I talked to him about this. How I felt and why. He understands that I would feel this way, but tells me I have nothing to worry about. He constantly tells me I'm beautiful, etc. He's hurt that I don't have trust in him. What can I do to get over this??? I'm not sure there is an answer. Time will have to heal - or help forget.
Any thoughts?!