Hey everyone, I'm Jack (Jack-Frank) - but my friends call me Frankie.

I've been thinking a lot lately.. mostly about me and my boyfriend.
We've been together for a few months now.. and he's really, really nice and sweet - and he's just a wonderful person in general.
Which makes this harder..
We've talked to each other plenty of times about me being transgender and he says that he doesn't mind it at all.
But here's the thing... he's completely heterosexual, I'm not..
Since I'm Transgender (ftm), we're technically in a homosexual relationship...
And so, I asked him what he would do when I started to present myself as male by binding and dressing male and packing and whatnot.. and he said that he'd honestly have a hard time with it, and that he was sorry.
I want to start presenting myself as male when school starts up again - it's my last year in highschool.
So, when I start presenting myself as male, there will be some difficulties in our relationship...
He said before that he sees me as a tomboyish girl, and that's what he's attracted to.. and that he hoped I didn't mind.
The problem is though, I don't feel as though we should, or can continue letting our relationship grow.. I don't believe it's fair to either of us to let ourselves become closer to each other, when I know that later, it will end because of me being transgender.. and because of me wanting to present myself as what I feel is my proper gender is..
I feel it's unfair to him because it feels almost like I'm taking advantage of the fact that I know that I look like a tomboy and that I know fully well that that is what he's attracted to..
But I feel it's unfair for myself, because he knows that I'm transgender.. and he even knows that it's next to impossible to look at myself before a shower or any time I have to look at myself.. without feeling disgusted with my own body... but he still wants to be with me; and he's attracted to the "tomboy" he thinks I am.. not to my male self.. which is, what I believe, my true self...
Part of me tells me to stay with him, that it's stupid what I'm thinking, that it doesn't matter... but the other part of me tells me that I really, really shouldn't... because it is wrong.
The last thing I'd ever want to do is hurt a wonderful person such as himself.. but I don't know what to do.
Please, I know it's probably a lot to ask... but I'm desperate, and I need advice.. What should I do..?
I know it's wrong to stay with him.. but, excuse my language.. I'll feel like a complete and total ->-bleeped-<- for ending it over something like this.. but I also can't help but feel as if "this" is a good reason..
I just don't know what I should do.. I'm confused.. and upset..
Please, I need advice... If you guys could help me on this, I'd forever be in your debt.. <3