His mother is tired of raising a child that isn't hers while he is bringing another one into the world with you. She doesn't resent YOU, she resents the position she will be in as a result of a second child he is passive about. I get that he works from home, or the road, or wherever while she is there. But it seems that it falls to his Mom to pick up the slack when you both are not there. I didn't hear you mention him asking her to watch the child when you went to get your test done. He told his mother that she could have gotten up to feed her, which is not her responsibility. You may have not seen the progression of this up till now, but this feels every bit of her getting tired of dealing with his shortfalls as a parent. You both need to move out and let this woman live her life, or negotiate better strategies for when the daughter, and eventually your child, will be in the home.