I'm disabled and now my fiance is about to lose a leg to cancer...I don't know if I can go through with this..?

My world has been turned upside down this past week as my fiance got word that his cancer has spread up his leg and bone at the top of his femur is dead and he's going to have to have his leg amputated from the hip down, and quite frankly I'm freaking out. I love my fiance more than anything in this world but I'm freaking out because I've been disabled since a car wreck left me paralyzed from the waist down in high school and now I'm having a really hard time imagining how we will be able to take care of each other since both of us will need help getting around and we'll both be using wheelchairs and neither of us will be able to do a lot of things for each other. I hate to say this, but the thought has been going through my mind that I can't marry this man now. I know I sound like a total jerk in saying this, but I can't imagine living the rest of my life with my disability and having my spouse also be disabled, and it's tearing me up on the inside that I feel this way, because I love him more than anything else in this world but I really can't see myself marrying another disabled person and I really don't know what to do. He's my best friend in the world and I know he'd be devastated if I told him how I'm really feeling, but it's the truth and I don't know what I should do. I haven't told anyone that this has been going through my head, and I'm scared. Any advice any of you can offer would be so very much appreciated.