Just not feeling it?

So at the beginning of our marriage my husband and I had a lot of sex, as most new couples do. But we’re not like 7 months into the marriage or something and I’m 8 months pregnant and he just hasn’t wanted to have sex with me. I feel so insecure. I know he could just not be in the mood but if I used to be like do u want to have sex he used to say yes and we would do it. Now he constantly says that he’s not in the mood. I just don’t know if it’s me.