Sex during pregnancy sucks -husband doesn't seem to understand

I recently became pregnant with my first child. I will be 31 this year and my husband turned 26 in May. Ever since I've become pregnant as you can imagine an array of NEW and UNCOMFORTABLE things start happening to my body, which I know was to be expected. The one thing I did not expect was to see my libido decline. This is due to the pain that occurs, even at 20 weeks pregnant, while having intercourse. I have tried to explain to my VERY active and used to getting it basically when ever he asked husband, that the pain is too much for me to bare at times. We have had many fights over sex because he feels like (I am guessing) he's not getting enough. We have had MAJOR arguments over sex. I don't know if I should just give in to him, or just tell him to pop off, go away and not worry about his feelings over it any more b/c frankly I'm tired of arguing over it like kids fighting over who gets the first piece of candy. It's not that I don't want it, it's just that it freaking hurts and yes I don't look forward to it. He promises time and time again, that he won't do certain positions that tend to make it worse, and like the fool I believe him. Then every time I DO agree, he ends up doing the positions anyways. I'm almost just done with trying sex altogether and avoiding the topic until this kid is out of me. I just want to be happy. I want my husband to be happy. I used to believe back before I met him (due to another relationship) that all MEN ever wanted was sex. He had proven me wrong about this, with the way he was. Therefore, I gave him sex whenever he asked almost. Now it's like the only thing he seems to ever ask me for days on end. He works with my OB's office (he is in sort of a nurse position at his job) that helps delivers babies. So it's like I don't WANT to air out our relationship details with my OB b/c of fear of embarrassing him. I just don't know what to do. Am I wrong for wanting to put my foot down? Or should I just suck it up and deal with it and cry for 30 minutes after every single time we have sex now? :(

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