Sex is a chore (explicit)

Hi mummies, I have a 5 month old infant, and I am not looking forward to sex with my husband. We have not had sex since my second trimester. Back story: I used to have high sex drive and would ask to have sex every 2-3 days. However, husband always complains he’s tired or it’s too late and promises to have sex over the weekend, but that don’t usually happen. We used to do it every month in the earlier stages of our marriage, then it became once every 3-4 months. I get tired of asking, to the point that I don’t enjoy sex with him anymore. Sometimes he have difficulty arousing me and he gets tired of trying when I complain of pain during intercourse. I do satisfy myself on my own without his knowledge. When we were trying for our first child, I would pretend that I’m ok just so he can quickly finish. Now we are thinking of trying for a second child, so husband is starting to initiate sex. Not sure if he really wants sex or it’s just to have a chance of having a child. I have rejected him as I dread having sex at this point. Wondering if any mummies are in the same boat as me. Would appreciate any advice! Would like to add that husband is otherwise a generally responsible husband and father.