Help! Mom is controlling my relationship

My boyfriend and I are rocky sometimes. He's not overly communicative on his feelings, but when he does show them it's been bottled up for a while and I get upset. We broke up and got back together and everything has been great. But we were talking and I got upset and started to cry.. my mom is giving me til Friday to end my relationship with him. I'm 21 but I still live at home. She's threatening to go down and break us up herself and that she'll cancel everything I own if I don't break up with him. I love him and I don't wanna do that but I feel forced. I don't know what to do and I can't tell her anything. It's like I'm trapped because I'm banned from seeing him if I get back with him or she's going to break up with him for me. I don't want to break up with him, but I feel I have to. All I'm doing is crying because of her. I don't know what to do...