I have been and currently am in the exact same boat as you (minus the ex part). As a warning, my advice isn't fun, but it is what worked for me, kinda.

Up until a few months into HRT, I used my penis to have sex with my partner. It wasn't the worst thing in the world, but I certainly didn't like it much. It solved the problem of I'm horny, she's horny, do this and we're not horny anymore. However, we had to take a break for a few months because surgery, but we did it eventually have sex again. This time, it sent me into a wild spiral of dysphoria that took me a while to recover from because of the exact question you posed yourself. "Am I even trans?" After recovering from that extreme spiral of dysphoria, I came to a solution. It was to simply take a secondary role in sex and not bother with my penis or my own pleasure. I simply pleasured her and when she finished, I was finished. That means I've simply not had any active role in sex for a long time now, but it also means that I'm not falling into deep depression because I used my dick.

This is not an easy mindset to get into and just straight up might not work for you. After all, I'm mostly a top with other women so it wasn't any sort of issue. I also garner pleasure from the pleasure of others. So who knows. It might work for you. I genuinely hope you do find a solution though. Your situation is a very unfun one to be in.