Question gay bros- married female here- I think my husband is bi

Ok my man has a fixation on butt play and transsexuals. I suspect he has been with men but he won't ever confess this. Now I'm very open minded as I try to encourage him to be sexually free just don't be sneaky about it. I've engaged in acts with him and a transexual twice.. I didn't enjoy It but I did it to make his fantasy happen and because I want him to trust that I won't judge him. And honestly.. I think he chose transexual because he's embarrassed to try with a gay man with me. Would I be open to it? Yes… it's just sex… but he all of a sudden doesn't even want I have these discussions… gets defensive when I bring up the fact that we've done 3 somes with Transexuals.. And he doesn't even like the idea if I mention anything with another man… BUT I know he watches gay porn. Transexual porn.. I suspect he engages in cruising.. I don't know what I'm asking by posting this— what is the deal! We've been together 13 yrs.. Married 6..its like now that I'm his “wife” I'm supposed to be a prude while he sneaks around.. I wish he'd be ok with saying he is Bi-... It would be so much easier.