24 years old, married 6 years, NO SEX LIFE

Charity
I am 24. I have been with my husband 9 years married 6 years, high school sweethearts. Anyways, for the past 4 years we may have sex(make love) three to four times a month sometimes less and sometimes not at all. My hubby is 25, FYI. I think it is because I haven't been able to conceive and I have gained about 100 lbs since high school, due to depression. I feel worthless, fat, ugly and that I disappoint him because I haven't conceived and I used to be skinny. I feel because I gained weight I disgust him.   feel awful because I never want to have sex and he is always in the mood. He tries to make me feel better but in my head he's only saying it to "get some." By the way he's not like that at all, I just think this. I don't know what to do... Please help me save my marriage. How can I get my sex drive back? Please help.