In a tough situation with my gf of 3 years. Need advice.

I've been with my girlfriend for going on 3 years now. We are moving in together. I go into spells where I am completely unattracted to her. She will try to kiss me and I basically lay there like a dead fish. I want to break up with her so badly but I always find that I need her support. She has helped me a lot and I do love her for that and I try to help her when I can. I have absolutely no urge to be with her for an extended period of time. In social situations I had to get over the embarrassment of being with her. She's a little bigger and I understand that but I wish I could find someone who is attractive. I've lost the motivation to exercise because I feel like there is no point. Anytime I bring up working out she just gets offended and gets angry. She also has some of the worst luck imaginable so at any moment something will inevitably happen to her and I have to support her which is usually 4 or 5 times a week. On top of helping her I have to be the emotional support. This kind of support is very difficult for someone who im not attracted to. I hate myself for putting her in this situation. It sucks but it just feels like im using her till I get a better situation. m-21 f-23

tl;dr Moving into an apartment with gf of 3 years in a few weeks, but not attracted to her and having problems.

edit1: Not a troll. Just was asking for advice since this has been on my mind for a while and I thought I could ask here. I haven't been able to talk to anyone about this which is why I came here. I would never cheat on her. I can barely keep a secret from her she knows some of these things because they have come up before and we talked about it but I wanted to try and see what reddit had to say. It feels like no matter what problem we have it ends up working out but these feelings keep coming up. I'm not trying to be a dick. Like I said I do care about her and there are times when she is in dire need of me and I make sure to come through for her.