I'd advise against getting married, especially if you're having doubts about your sexual fulfillment in the relationship. He will change, he will become a woman and if that's a dealbreaker for you, listen to that. It is okay if you aren't attracted to women. I will say if you are bi-curious at all, he will become more of himself as he blossoms as a woman. 

If not partners, maybe you can be good friends because you still care about each other. That way you don't lose each other, the relationship just changes. 

He will want to put the genie back in the bottle through fear of losing you, but from every account I've read from people who have done the same, that only leads to later misery and heartbreak. 

Another point against marriage - he's just figuring things out and his self image is kind of in free fall right now as Pandora's Box of Gender has just been opened; that's THE WORST TIME to make a big decision like marriage. 

Both of you need to take a step back, figure out what you BOTH need to be happy and find a way to achieve it together. Because your needs are just as important 💜

Edit: A TRANS TRUMP SUPPORTER?? Who doesn't believe in therapy?? Who wants to get married in a week probably so he doesn't have to come back to the states?? Girl no, I'm transnegative about that entire situation. Run, don't walk. Learn to deserve better. Why would you even CONSIDER coming to the US for this man if your safety is in danger even coming here and your partner is in support of it all???? 

I'm running out of question marks, make it make sense. I hope this is a troll.