I'm desperate

My husband doesn't feel like having sex😞
He says he might me sick or something but he never go to the doctor. We have sex once a month. I feel ugly because I can't turn him on. I'm desperate because I want to have sex with him. We have been married for 3years. I don't know what to do. I know he is not cheating because he is always on time at home. He is 30 and I'm 27