Sexuality is no easy thing, even for people who say they hardline straight or gay. I currently have 2 partners, one of a year and a half(Jared), and the other of 6 years(James).
Jared is very much into both women and men, so my transition is exciting for him.
James is only interested in men, but I still have my penis and a fairly masculine body, with A cups...but he is interested in me still. I think that will probably not change. But we have one less thing to worry about, none of us are monogamous.
It sounds like you are getting pretty jealous, so I think you should have a sit down with him, if the way he refers to you upsets or invalidates you, tell him. Explain clearly how you are changing, and feeling. Maybe it will work out...but if it doesn't, I'm sure you can find someone who loves you for you :3.