Am I just no good anymore?

I have explained to my husband that I can only climax in the missionary or cowgirl position, so why won't he give me missionary unless I force him? He sometimes wants me on top, but he usually only ever wants me on my side or stomach. I can't even get or keep him hard, he usually has to make himself hard but as soon as I touch him or he goes to penetrate me, he loses some of his erection so I'm usually getting a semi hard penis which is both uncomfortable and painful. The other day I saw a post from his brother that said "if a man fucks you from the front you got good pussy", so I mentioned it to him, he didn't say a word and still, a week later, won't give it to me in the missionary position.

This is my fav position because of the closeness and the masculinity he portrays and what's crazy is that before him, I hated this position! Anyone I was with before him loved my pussy and couldn't get enough of it. I've had men who told me they could only do me once or they'd end up marrying me, my ob says my vaginal walls are exceptionally great, and I didn't so much as even masturbate for the past 2 years while he was locked up, so why won't he make love to me in my fav position? Has my pussy become no good? Is he just not into me? It's to the point where I do not enjoy any part of sex with him, he doesn't make me feel sexy at ALL in fact just the opposite! I have even seriously contemplated allowing him to be with other women but if i do that i will litetally have to fall out of love with him and I would never want him to touch me again which would subsequently end our marriage. I'm 4 months pregnant and so freaking horny I desperately need to have some orgasms but he doesn't seem to care if it feels good to me one bit. What should I Do? I'm obviously not good enough. :'( Please help I'm so depressed. :,(