His mom doesn’t like me.

My boyfriend and I have been together for a year and a half (I’m 18, he’s 21). I met his parents and his sisters a few months ago (he’s the only boy). His dad and his four sisters like me, but his mother is a different story. You’d think that because he’s the only son, he’d be a mama’s boy. Well it is the complete opposite with him. His mother prefers the daughters over him. He told me that his oldest sister would bring home a new guy every week and his mom would be all over them, wanting to get to know them. I’m the first and only girl for him to bring home to meet his family and she didn’t try to get to know me at all. My boyfriend tells me that he notices the same thing about how his mom acts towards me and tells me that the way she acts towards me mostly has to do with how she treats him, and that I’ve done nothing to her to hate me. I just don’t feel welcome in their house whenever she’s there because she doesn’t talk to me or even look me in the eye. I feel invisible when I’m around her. I’m here visiting my boyfriend right now and about 5 minutes ago, she walked through the front door coming from the store. I smiled, waved and said hi and she looked at me, didn’t smile, and blew me off. I just don’t know what to do at this point.