I'm an ftm, and I've been doing long-distance for six years.
It can work. You just need to make time, every day, to communicate. Otherwise "out of sight, out of mind" starts to creep in, and it's easy to fall out of love. Communication can be chatting online, talking on the phone, sending an e-mail, writing a letter, jotting down something you want to mention next time you're able to talk, or anything else that focuses your mind on him and encourages you to interact. I find the best advice, for anything that goes wrong, ever, in an ldr is TALK ABOUT IT. Don't bottle it up. Don't save it for when you're face to face, because then you'll be trying so hard to get the most out of the little time you have with him, that you might not want to bring things up that will "ruin" it. Talk about it now, before it becomes even bigger and makes one or both of you resentful. The thing about ldrs is you aren't seeing each other every day and seeing the ups and downs of each other's moods. So from one partner's perspective, it can look like the other is having a ridiculous mood swing, when in reality that partner's frustration has been growing steadily over the past week and just now reached a tipping point.
That's just basic advice for any ldr. For trans in specific, I'm not really sure what to do, except get him talking about how he's feeling every so often. There's a fine line between pushy and concerned. I've never met him, so I don't know how he feels about the whole sharing thing. I try to keep my bf in the loop. When I don't, bad things happen--misunderstandings, miscommunication, resentment, etc. But your milage will vary.
Also, don't be afraid to try sexting, talking dirty on the phone, and describing fantasies in online chat or e-mail. This may seem like a TMI, but it helps keep the love life going when you're far away from each other.
Best of luck!
