Ok...you came clean about your A 2 years ago, but obviously your H is still in a great deal of pain over it. It takes everyone different lengths of time to heal from a wound that deep. One thing I'd like to kind of clue you in on that I think your H could be struggling with is well...as you mentioned kissing.
Kissing for many people is one of the most intimate acts you can do with someone. No offense intended here, but there are many hookers out there who have sex, but refuse to kiss someone on the mouth. Many people can in some ways disassociate the physical act of sex from actual intimacy, but it's very difficult to disassociate kissing from intimacy....I think this is what your H is struggling with.
The sad fact is....as you say, the ONLY thing you did with the OM is kissing....the ultimate intimate act to many people. Your H refusing to kiss you tells me he's one of these things #1 afraid to be intimate with you because you'll hurt him again and he doesn't trust you, or #2 withholding that intimacy from you out of unresolved anger.
It's a good thing the two of you are in MC right now, that's really where you two should be IMPO. Has this issue been brought up in your sessions?
