Chippermonkey is right. Your man should be sticking up for you more. Something is definitely strange. I don't think you need to trash your marriage though.

If it were me, I'd take both him and his mother to an experienced counselor and participate in family therapy. Clearly his mother has some sort of deep issue that needs to be addressed. It could be that she feels abandoned by her son (is she divorced by chance?) and lonely. She sees you as the enemy, stealing her man so to speak and will continue to do so until you two can learn to share him in a healthy way.

Also, mommy dearest needs some therapy of her own so she can go get a real man instead of leeching off yours.

Again, there's no need to give up, but it seems there is a need to seek some professional help. Your husband needs someone to glue his balls back on and therapists are pretty good at that (especially male therapists.)

Hope that helps!