Long distance plus bigger problems.?

I am in a long distance relationship with a girl. We have been talking for about 9 months. We say we love each other and i think i do. I really love talking to her and sharing things from my life with her. i already broke it off with her once but we are back together. It is becoming harder and harder to go on with this relationship. I want to be with her but i think it isnt going to work. Also she has a degenerative muscle disorder and it is worse then i was lead to believe. I dont know if i could deal with having to feed her in the future. I dont know what to do. I dont want to loose her but on the other hand i have these doubts and don't think it is fair to her to keep going on. Im LOST! i just dont want to **** her over