My mother has sever depression and dementia?

good lord!-i dont know where to start-so here i go, my mom is 50 years old and has suffered from sever depression since i was 6-im now 31..and has suffered from dementia since 1992. i take care of my mother-atleast i try my best to-i have children 2 youngest stay with there dad and my oldest is with me who is 12....i did research on dementia to get a better understanding of it.-dont get me wrong, although my mother was unfit when i was younger-i do love her, but her mental illnesses has taken its toll on my life. iwant to get married and move onwith my life-i am pregnant with my 4th child and my mom still lives in the same household. my issue is, im tired of dealing with it. i dont want to spend the rest of my life taking care of her. i have enough stresses throughout my days and hers just makes it harder...my moms mom-who is 72 years old is ill and wont be here much longer-3 years tops if that, and when she pes away im afraid how my mother is going to react to that with her mental