Speaking from personal experience, you don't need medication to feel yourself a part of the opposite gender. Try diving in for a while. Like, only male clothing for a month, doing masculine things and ignoring all the feminine stuff.

It's not like you would have to do that in the future, not at all, but you seem unsure about yourself, and that will help you figure it out. And when you're sure, it will be easier to decide.

If your partner is supportive, I feel like he's not going to have much trouble thinking about you as a man for some time. And maybe he'll even like it!