Fiance not attracted to me because of weight gain

So over the last two years I have been diagnosed with a condition that requires me to take weight gaining medications. I went from super fit to fat. Tried everything from meal prepping, HIIT , weights, running, and etc 5 times a week. I used fitness pal to keep track of my calories. kept it at 1200-1300 calories a day. many times I found myself crying before work because I could figure out why the weight wasn't coming off. I have always been a fitness fanatic. during this time doctors found multiple fibroid in my uterus. they got so large my belly swoll up to the size of a 18 week pregnant woman. I hated myself and didn't recognize who I was. going through this alone was frustrating especially as coworkers teased me because of my weight. I thought my fiance loved me and was the only person could confide in. well that changed tonight as he pointed out he isn't attracted to me and doesn't want to have sex with me. before this I thought he was different. I have never felt so ugly in my life. half of me wants to get a knife and cut the fibriods out of my belly and starve myself. I have just been crying all night. it kills me that you stand by a man when he's unemployed, short, and broke but he puts you down at the worse point of your life. I know I will eventually lose the weight but I will always remember this feeling. the day I realized that love is conditional and fades when you aren't at your best.