Cheating?! MIL not being supportive!

I really need opinions and advice on this issue. My husband and I have been together for 6 years. He had two kids with a girl back in high school who he never married. The kids are now 10 & 11 and I have been like a mother to them when they come over to our house. Well, my husband lied to me and cheated with the kids mom the first year we were together. I found out through messages and pictures. I forgave him, moved on and everything immediately changed with him. He only talks to her about the kids, married me, has given me my place which he never did before, and we are now expecting our first little girl (he has two boys). My MIL has pictures of the kids mom all over her facebook. Pictures of him with her at MY HOUSE celebrating her birthday which is a few days before mine🙄😒, pictures of them celebrating mothers day, his birthday, fathers day, CHRISTMAS at MY HOUSE! He created fights on all of those holidays and kicked me out of my house so she can come and hide all of my stuff! I didn't know until I saw messages and did a lot of serious investigation lol! Well, I forgave him. My mother in law would not delete any of those pictures which are pictures of him and her CHEATING on me! They are not pictures of my mother in law and her or family. They are pictures of my husband CHEATING! I have never asked for them to be deleted however he has asked her and she would tell him that even though they are not together, my mother in law still respects her as the kids mom and would never turn her back on that girl. But where am I stand then? I am his wife and also the mother of his child. My mother in law thinks I'm just crazy😑 she has never posted pictures of me and him together or the baby due to the respect she has towards that girl who was only his girlfriend in high school! I feel disrespected and honestly humiliated because all of his family sees those pictures and how can I explain to everyone I have been with him for so long and those pictures are a year or two after we were already living together. Please help me! I feel very resentful and don't really want her in the room when I give birth but I don't want to be selfish either. Thank you!