My mil took my son from me now he hates me

My mil took my son from me at birth and moved to another country. It took me several years to get him back but that was only because he needed to attend school and couldn't do so without my permission. Even when he started school, every weekend and holidays, my mil would just show up at my house and take him home with her. They would cause a scene and my son will cry wanting to leave me and follow her. Years passed and I eventually gave up as my son grew up hating me because my mil told him that I'd thrown him away at birth. So he only wants her. I gave up and told my mil I would get an official order for her to adopt him so he can be with her always. My MIL immediately returned him to me and never came by or called ever since. But at every family gathering, she would pull him aside and whisper things to him. The whole family has done and said many things to stop her but she wouldn't listen. And everyone tried talking to my son but he also wouldn't listen to anyone else but my mil. Nowadays, bcs she doesn't come to see him or take him home, my son throws tantrums. He would spray water on our kitchen floor. Slam things around. Break things and tear our sofa. He even hit his older sister and younger brother. He also punched me one time and tried to kick me while I was pregnant. I suffered miscarriage before. I am pregnant now again and I can't really handle the stress. I can feel my stomach hurting everytime he does these things. I can't take it anymore. My husband has tried many things too but he won't listen. He's giving us problems not wanting to go to school and the school thinks we're abusing him instead of listening to the problem despite our several attempts at explaining. He is 11 now and I'm worried things will only get worst from here on. He only wants his grandma and that woman has been whispering all sorts of bull about me n my husband to him. My mil had a problem when she was young. She loves kids but could never have them. So she started adopting kids. We only found out after she took our son that she had done the same thing with my husband and his brother. She took my husband away from her SIL (who is my husbands biological mother). She has a condition which no one spoke of and she doesn't seem to think she's doing any wrong. She keeps telling me I should be grateful for her bcs no mil would help to take care of my child like she did. But the biggest problem now, is my son seem to think I'm the devil who separated him from the only person who loves him. Can u believe he is 11 and doesn't know how to eat and shower properly on his own? My mil did everything g for him and spoilt him so badly. I just don't know what to do. I tried seeking help with psychiatrist and social services but none followed up. My son seem to put on a show in front of others and that's a scary thing to me. The whole story is alot longer. But I had to summarise. My husband and I are completely at a loss and don't know what else to do.