I NEED URGENT ADVICE FOR TONIGHT

so, me (17) and my guy (18), are together don’t call each other boyfriend and girlfriend etc because even though we treat each other like that, i have negative experiences from relationships ie my parents divorce and my mothers experience of abusive relationships, ANYWAY. me and my guy we are supposed to be going to look at a uni a couple hours away next week, he said it would be easier if i stayed at his the night before so it cuts out a bit of the journey as my house is out of the way, his mum is fine with it and has encouraged it. we have a very strong back ground (being friends with each other since i was 9 and he was 11) but i don’t know how to approach it with my mum to ask, because of her experience she is very protective and quite sceptical of everything. but the thing is, she has always treated me like an adult and i’ve took that, caring for my little sister when she couldn’t, doing various chores, even helping her with financial situations. so she cannot justify that i’m still a child when she has always treated me like an adult when convenient to her

any advice would be amazing!!!

thank you