I can't give you any advice, but I get it. I can't get turned on if Karma smells of her perfume. And I have a personal distaste for hickies sooo everytime he comes home with one I'm a mess. My big issue has always been if he's with someone but can't sleep with them, then comes home to me. I feel like a sceond rate prize.
I'm sorry I know it isn't helpful, but I just wanted you to know I get it. I don't have an explanation, but I understand the feelings. I don't particularly have compersion for Karma and his g/f, so maybe that whole comfort in the relationship theory has a lot to do with it. If he snuggles with my wife ( a very close friend of both of ours) and he comes home smelling of her, that doesn't bother me.