Partner seems to have lost interest

Mainly a rant but also if anyone has any advice I would really appreciate it ! LONG POST ! APOLOGIES Me and my partner have been together almost 4 years, living together 2 years. Two kids, my 9yr old son and our 5month old baby. When our relationship started out and during the time we didn’t live together I felt like he couldn’t get enough of me. He was relatively spontaneous with sex. As time went on it started to feel like he was always in a rush. Just wanting to get straight to penetration then done. When we first moved in together things changed and it got back to that exciting, spontaneous, generous sex. He seemed like he couldn’t get enough when it came to pleasing me. November our first year living together I found out I was pregnant, something we had been planning and both wanted. I had a rough time at start which meant either being sick or sleeping 🤦‍♀️ A few months in and things got better, I started feeling like my usual very sexual self. What I soon realised is that he just did not feel the same way. It started getting to be weeks without any intimacy at times an entire month. We discussed and he said he just wasn’t sure if I would be in the mood or not depending on how I was feeling. I told him that me not wanting to would very rarely ever be the case as I have an extremely high Libido. Anyway things got slightly better, then bad again. Soon found out he was watching a lot of porn and had even made an onlyfans account to watch content. We talked and had a plan to work on things to get better. He said he had a problem with porn. Anyway fast forward through the pregnancy and not much changed in terms of sex and even the porn. In some ways got worse. I started to care less and just gave up focusing on the pregnancy. Present day and our daughter is now 5 months. I can quite accurately say we have had sex about 4 times since I had the baby. I also found yet another load of evidence of him watching porn when baby was a couple months old. I just feel like he has no interest in me whatsoever ! The few times we have had sex it’s been all about him and his pleasure, then he’s done and ready to sleep. I feel so unattractive to him, like he just sees me as the mum to his child now. We have had plenty of conversations and it always ends in him saying that things will be different and he will make more effort, but I never see this actually happen. I just don’t know what to do anymore