I wish I were a girl but I'm still straight. How do I talk to my girlfriend about it?

I have a very complicated situation, and I think I should start from the beginning. I was born as a male, but I have never at any point in my entire life felt right about it. I always wished that I were a girl. I've always felt like my birth cirstances were a mistake. One of my most common fantasies throughout my life was of one day just suddenly turning into a girl. The fantasies were always different. At very early ages when I still believed in a lot of things, I hoped I could get fairy godparents that would grant me the wish, or I hoped to find a genie in a bottle, or to find some ancient relic that would grant me a wish. I would wish to santa that he would make me a girl (somehow). As I got later into life the fantasies didn't end, they just changed their nature. The eventually became fantasies where a new, cheap change procedure gets developed that will turn you into a fully functioning female and everybody is supportive and just wants me to be happy. By the way, by fantasies, I mean nothing ual. Another word for them would be "daydreams." There was a period of time in junior high when I was starting to get adult hair. I would shave my legs and underarms and everywhere using stolen razors, and no one noticed because I never had the hair before. All throughout my entire life I wanted to be a girl. Sometimes it was just a little notion in the back of my head, something that came up when I saw pretty dresses I wanted or I saw very graceful, beautiful female character in a show or somewhere. Other times it was a constant overwhelming desire that dominated every aspect of my life. I'm actually straight despite all of this. I am attracted to women. I've tried to figure out if I like men, but it just doesn't appeal to me. During one of my very bad bouts of longing/desire, I was hanging out with a lot of girls and fell in love with one. A few months later I began dating her. Dating her kind of pushed some of the feelings to the back of my mind, I was able to sort of live vicariously through her. Here's where it gets to the problem. Recently I'm having one of my serious times where it takes over everything that I do. I'm letting my hair and nails grow long and doing different things with my hair and clothes. I have experimented with various bows and such in my hair. I've tried to make myself more feminine with diet. I have been consuming foods that are high in estrogen, estradiol, and testosterone suppressors. I have also been avoiding foods that limit estrogen. I have consumed some very disgusting mixtures in my attempts, one consisting of fennel, soy sauce, raw licorice root, and nutmeg. I nearly threw up the times I ate that. I'm so desperate that, despite no readily apparent changes, I keep this up. And the problem is: I want to tell my girlfriend. I love her and I want her to accept me. We've been dating for years, and I constantly fantasize about a coming out moment with her where she is extremely accepting and tells me that she actually always wanted me to be a girl, but didn't want to say anything. I try to stop myself from thinking about this, it just depresses me when I think about how ridiculous it is. There was one time where she talked to me about how she thought that I wanted to be a girl. At first I was going to come out with it right then, but I realized that she is actually very uncomfortable and unhappy with the idea of it, and I had to keep on with my guise. My question is, what do I say to her? Will she ever accept me, or am I going to have to lose her on my quest? There's no question of it now, no matter what, I have to get the change. I can't take it any more.