Hmm, well, if he believes that the cessation of your sex life is because you might be gay, then of course it will come as a rude awakening to him to find out that, no, it's not men, it's just that you don't want *him*. I know I'd be hurt in his position, and I might not be able to carry on in the relationship. However, I think you should tell him. He deserves the truth. And there's every possibility that he will still consider the relationship worth preserving, just as he does now, as a non-sexual partnership. Maybe he'll deal just fine, either right away or after a little time to recover. It's a risk. But it's worth it to be honest, imho.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.