Suddenly sex was different. Need advise. Am I the problem?

My boy friend and have been together for almost 9 years! The sex was always amazing. Had a baby in 2020 and after I recovered nothing changed and that made me happy. 2022 happened and the sex got mind blowing.

I had our second baby late 2023. Everything was great until 3 or so weeks ago. Now after we have sex I think “yeah that was for him because I don’t orgasm” it don’t feel bad it just don’t get be there. This has never been a problem before and I don’t know why!

We had a discussion yesterday, briefly discussing it amongst other things. It got heated but then it got better. We had sex this morning and still no orgasm.

Is it me?

I kinda feel like he doesn’t last a long as he used too.. but then I don’t want to complain because he does most of the work.

I think I’m hitting sexual frustration and it’s incredibly stressful on top of the other stresses.

Please help. Advise??