my parents don't support me at all

i feel really stuck and trapped. my parents have me take care of their kids all day, and hardly allow me my own life. my mom told me that going outside was privilege and not a right, even though i'm 18. i listen to them and i follow their rules, even ridiculous ones i don't understand but i do it out of respect. my dad is never around so he doesn't really care, and my mom gives me support only when i do something she's happy with. when my attention is completely on her and the house. i recently got a boyfriend and i would like to sleepover for a night. i take care of the kids everyday and put my mental issues to the side constantly to take care of them, but i can't always do it and sometimes i need to get away for more than just a few hours. my boyfriend doesn't even want to do anything intimate he just wants to have me over for longer than a day, and he respects that i don't want to do anything, but my mom is still not budging. him and i think it's a matter of control and that it isn't about sex at all. otherwise i wouldn't be able to go for several hours unsupervised. she said she wanted me to go out and be more independent and then i try and she shuts me down with all of these rules and regulations, and still forces me to adhere to her schedule. my therapist said that it's a good idea to push back a little, and understand that i'm an adult who can make these decisions for myself. she also said that it's worthwhile to consider if certain things my mom does is to protect or to control me. it's just irritating. they won't let me have my own life now that i want to finally get out of this really bad period of intense mental deterioration and they're not letting me