Hi, I believe I can help you.
It sounds like your boyfriend is not considering your feelings about this situation. He should not be in contact with any of these women, especially while he is with you and even if you have trouble with your relationship.
By cheating on you and allowing these women to have access to him, your boyfriend is undermining your trust. And without trust, a relationship cannot survive. There is no way to continue together as long as you have to question if you can trust him.
The topic keeps coming up because it is not resolved. He needs to admit he was wrong and make this up to you. If he cannot do that, then the chances the relationship will last is low. He needs to earn your trust back and until he does that, the issue will remain an problem.
There is a lot of deception going on in these relationships with married women, broken promises and cheating. Your boyfriend needs to cut himself off from these women right away and work on your relationship.
Talk to him about seeing a counselor together. His Aspbergers may be a factor but he also needs to learn to control his behavior. You can also work on the trust issues as well. Ask your doctor for a referral.
You can also learn more about infidelity and how it affects your relationship. Here are resources to help:
Transcending Post-infidelity Stress Disorder (PISD): The Six Stages of Healing by Dennis C. Ortman
Not "Just Friends": Rebuilding Trust and Recovering Your Sanity After Infidelity by Shirley P. Glass and Jean Coppock Staeheli
Infidelity: A Survival Guide by Don-David Lusterman
I hope this helps,
Also, you may want to consider seeing a counselor yourself if you feel your boyfriend will not go. You need the support right now to help you decide how to handle this problem.