As to the first concern, you should trust him to handle it in the way that works best for him. After all, he knows her better than you do.
But I believe the second concern is your real issue. If that's correct, you have to be honest with him about your doubts. Tell him that you love him, and that you need reassurance that he also loves you. Ask him to let you know if he has doubts about you as a couple, or if he is interested in anyone else. I think he'll reassure you that you're the only woman in his life. If so, trust him to handle the situation in a way that works for him.
John Gray is the author of “Men Are from Mars, Women Are from Venus.” Send email to www.marsvenus.com. All questions are kept anonymous, and will be paraphrased.