How do I take a stand to my mommasboy mother

After being in a relationship for about two years, his mother has been nothing but a bully, intimidating, rude, minipulative person towards me and my family. Although she is staying with me and my bf, she continues to walk all over me. Every time I try to defend myself I'm always wrong for it. Even though she's the obvious wrong person. I don't know what to do, she's taken over our home and has us seperatly sleeping in the living room...