Your fiance is probably an abusive greedy narcissist. Married men who have sex with men like your fiance 1) are out engaging in MSM behavior without condoms 2) are out engaging in sex without you leaving you horny 3) are putting your life at risk HIV is a major threat to you 4) are spending money on hotels and prostitites for their MSM sex instead of paying bills. Instead of trying to understand him, and get him to admit it to you, do this instead:
1) Know in your heart that your man cheats on you with men, 2) Stop having sex with him (even with a condom) and do NOT let him give you anal sex, 3) Tell him that these are the new rules and terms of the relationship. Even if he admits it to you, it doesn't mean anything. He has put his own needs in front of yours, he's not monogamous with you, he cheats on you. You are just roommates. If you want to kiss him, that's on you. If you want to keep letting him have sex with you, look up how high the risk of you getting HIV is, astronomical (pun intended).