Is it a wife's duty to have sex with her husband?

Been married for 25 yrs. Sex was great in the beginning. Over time it got less and less. We discovered along the last 10 yrs that my husband suffers from depression. He says it is 85% my fault because we don't have sex. In the last 6 years I have had medical problems which have hindered me from enjoying sex and medication that has dropped my sex drive to nothing. I'm not interested in sex at all partially due to the health issues and also because everytime I show him any affection at all, he insists on us going all the way instead of just accepting what I am able to give. It is a huge turn off for me and makes me feel like unless we have sex, I can't satisfy him. Tonight I did something sweet and nice for him which didn't include sex, but he made me feel really uncomfortable by grabbing my boobs and telling me that they were his and he was gonna .... well I felt like an object. I pushed him away and he got all upset and then wouldn't talk to me. When I tried to explain to him how he made me feel....he crawled into his "depressed shell" like he always does and tried to make me feel guilty. He told me I was responsible for all his depression because we don't have sex. I ended up just giving in and letting him do his thing, but I felt like I was being raped and felt as if I was nothing. My mind isn't in it. He also says that I make excuses because I physically can't do things in the sack yet I do them when I do other things. I said, ok well I do what I have to in order to get things done, but my physical health suffers when i do, I'm down in bed for a week sometimes when I do things I shouldn't. So does that mean I should over do it in the sack so he is satisfied and then I suffer needing pain meds? I know we have some issues, but seriously who is right here? Should I be just giving in and letting him do this? Is it truely my duty to give him my body?