Sex is a Chore

My husband and I have been TTC for about 5 months. We were really sexual at the beginning of our relationship, but after 5 years things have died down. I want sex way more often than he does and even before TTC this became an issue in our relationship. We had some painful discussions about how he doesn't have much of a sex drive and has become self conscious (he put on a lot of weight), but he doesn't do anything about it to fix either thing like go to a doctor or make healthier choices. Each month has created more and more stress on me and our relationship. This month was the worst. I didn't tell him about my fertile window because last time he said he felt a lot of pressure and that was affecting his ability to perform. This time he got frustrated that I didn't tell him, and blamed not knowing on why he shut me down 3 out of 4 nights when I tried to initiate things. Today we worked all day in the yard, but I am ovulating and knew it was my last chance. We went to bed, he brought it up, said we needed to do it quickly because he was so tired and had to get up early, but then he wasn't really into it - very minimal effort that didn't make me feel sexy at all, it made me nervous. I didn't get wet right away, which he must have noticed because then he went limp. He sighed and got frustrated and started helping himself out. I kept trying to continue but he wouldn't really kiss me back much, so I took that as a sign to back off. But then he got angry that I stopped, told me it wasn't going to happen now, blamed me for the whole situation, refused to admit anything was wrong, and put his pants back on. I am at a total loss. I want this to be a fun and loving process, not a miserable stressful one. But how do I fix someone else who doesn't seem willing to accept help or fix the situation? I am starting to think this is putting a major strain on our relationship and I am worried about what will come of it. Has anyone else been in a similar situation? Any advice? I am so desperate for a solution.