He could be bisexual. It doesn’t mean he’ll go cheat on you. And there is nothing wrong with people being bisexual BUT What’s concerning though that he says it now. If he had interest in men he knew it for awhile/always and why didn’t he say something? He only now started liking men? Really? It doesn’t work this way

My daughter is bisexual, she had about equal number of partner of both genders, including long term cohabitating relationships/marriage with both genders. When she meets potential dating partners, she immediately informs them of her sexuality. Like on a first date. No one had issues with that so far but she is aware that some might object and they have rights to do so that’s why she says right away.

I also have to say that there might be a reason your husband is sharing it now. I’d talk to him more. But if my husband told me he likes men NOW few years after marriage I’d likely divorce him. In my opinion if he likes men I’d need to know on the first date not years later.