I want a baby so bad

I want a baby so bad it's making me depressed, all I've ever wanted I've been to doctors and they say it's Because I'm to fat I'm a size 20 ,, I no bigger woman to ofhad children, I'm 24 years old, and been with my fiance 5 years and nothing worried because all the mention is my weight I want a baby so bad and think it would make us complete