Advice needed (My Mom)?

I left home when I was 17, because my mom use to abuse me for just leaving dishes in the sink. I had to wear clothes twice my size or I would get punched she use to tell me she never wanted me so I got tired of it and left to a different city with someone.I'm 22 now and I just had a son and now with an amazing man .The thing is when I use to date my mom would ask my bfs for money or me and I would always give it to her,I even owe the IRS because of her and she yelled at me cause I couldn't give her the rest of the money.Well,on Mothers day my bf took me to a nice hotel .He told my mom he was going to take her out to eat but my mom wanted him to take my 5 siblings too so he said i'll see if he had enough.He tried to explain we only had enough to take her she went off calling me selfish ,"she wish she never had me" start hitting my boyfriend while he was holding my son..and kick us out of her house mind you we live 50 mins away from her but shes still calls me names tells me im selfish and I try to do everything for her ,like i dont have a license and she wanted my bf who was at work to come take her to the hospital when i told her we cant she just went off on me ..I still say yes ma'am to her my sisters who are 16 and 17 they have it easy I never heard her once say anything mean to them they wear tight clothes they bearly listen to her ,my 5 sibs have the same dad I'm from a different father but now her birthday is tomorrow shes like" Give me a gift i want something from you and him I deserve it since your so selfish ",she wasn't even saying it nice! I bearly work ,my bf pays all the bills plus we have a son and she calls me selfish all I do is give her respect and she goes and talk bad about me to me lil sisters and i hate that ....it hurts so much and I tried talking to her she feel sorry for a little but then the next day she yells at me and now Im grown all I ever do is try to please her. I don't want to do things for her just 'cause I don't want her to be mad at me I want to do it because shes my mom and i want to..I think she feels like just 'cause shes my mom I have to give her respect .When I try talking to her about it she says its 'cause I left home that's why shes that way but she was that way before! dont know what to do I want to keep are relationship but shes caused me stress when i was pregnant,and before that ! I mean im shock my bf still with me...she treats me like a little kid,she doesn't even do that to my sisters....and there kids but like i said i never talk back to her I give her respect no matter what but Im getting tired of getting treated this way when I love her so much .She tries to be nice some times so I would bring my son over her house but then she goes back mean ...Idk Im stressing to much