Ive been told i have not long to live?

my diet is so bad, im not over weight btw but i cant eat 99% of food, and my doc today told me i will be lucky to live till im 40, i am 21 now im so confused as to what to do, ive tried eating better and ive tried being hypnotised but it wont work, i cant eat food, i worry about when i want a family, ad how i wont be able to support them and watch my kids grow up