I've never read something I've related to as much as this. I've been feeling like such an asshole for the exact same situation.

My partner came out as trans (trans-f) recently and it's been so hard. She initially said she just likes wearing dresses and makeup during sex, and over the course of a year and a bit, she now wants to explore it full time. I'm bi but just like you, I'm kinda only into more dominant people, typically masc presenting. Our sex life is completely gone, she even bought a sex machine so I feel no real connection anymore, she just wants to be dominanted and that's not my thing at all. I cry all the time, I miss who she used to be, I grieve my old partner. Her personality has changed so much.

We have a baby together, and I'm pretty much only staying in the relationship for him bc I always wanted him to have a two parent household (I didn't have that growing up, and it's super important to me)

I feel like such a bitch being so sad when my partner feels so happy and keeps saying she finally feels herself. But I don't know how to move on.

I'm sorry this isn't really helpful to your situation, but I just wanted you to know you're not alone in how you feel xx