Left alone in my marriage

I’m 45HLF, married to 49LLM. I would really like suggestions and thoughts on our almost completely vanished sex life. We’ve been together for 24 years and have four children. Our sex life has always been quite vanilla despite my attempts to bring new things to it. Also it has never been as frequent as I would have liked. I’ve always thought, that my husband has rather low sex drive, and he actually said that to me (for the first time) just recently.

Our youngest child was born when I was 38 years old, and after that I had this spike in my desire for sex, probably because of the hormone levels settled down after pregnancies and breastfeeding periods. That spike of course led into even worse mismatch in sexual needs between us.

In the last few years we’ve been having sex less and less. It’s went from once a week to the point, that we’ve last had sex six months ago.

I’ve been patient but I feel that my limits are getting really close. I have suggested sexual therapy without success. I have talked and tried to get him understand how this really matters to me. He finds these conversations very uncomfortable and tends to shut down. My mind has obviously been through all the possible scenarios from cheating to porn addiction, but those just don’t feel plausible to me. Even when young he wasn’t that into sex and never cared for watching porn.

All the thoughts and suggestions about how to make this situation better are really welcome!