trans fiancé?

Te
A few months ago I made a post about my fiancé coming out as gender neutral. I am in complete support of him being who he is. I will always love him for who he is and will always support him. My problem however though is that when I first met him and up until now this hasn't really been a thing he's talked about. He never said anything about not liking to be referred to as he/him until recently. He has always been feminine but it was just that. His personality. Not his gender. Now he's saying he's not sure. He says he just doesn't feel like a boy. He's not sure though if he's a girl, but it seems like that's what he's leaning towards. He also said there's something serious he wants to talk about he's just not ready to talk just yet.
My problem is that I'm not sure what I would do if he came to the conclusion that he felt more female. I met a guy. I started dating a guy. I decided I wanted to marry a guy. Now that's all changing. I know that it's still him and that I still love him and that will never change, but it's still a lot. I'm not sure if I want to be married to him as a girl. I don't know what all these changes will bring in the future. It's not a matter of if I am supportive of the LGBTQ community or not because I could never not be, so please don't think I'm not. I'm just not sure if all these changes are the right life for me.
What do you think? Suggestions?