Sex with my husband

I have been trying to fall pregnant for a while now and every time i tell my husband i am ovulating he said he is tired and not interested in having sex. Even on his days off he will not be interested and it doesnt matter how many hints i give him. When we do try to have sex i can feel the moment and then he goes soft and small and its all over. I am going to the gym to loose weight and i am lucky if i have sex once a month. I told him to take the tablet the doctor gave him or watch porn but he doesnt want to do anything to make the situation better. I asked him if he is cheating on me and he said no amd there is nothing on his mobile. I asked him what the issue is and he wont talk to me and always say there isnt one. Can someone please help me figure this out.