<human>: Can you provide a brief overview of the text?

A little background:

I turned 18 less than a week ago and my goal is to finally get freedom to take my own decisions concerning my personal life. I've been together with my boyfriend for more than 8 months and since my mother is highly over-protective I have not been able to sleep over at his place yet. He gets to sleep over when he's at my place but only if he's in the spare bedroom downstairs. That I don't get to sleep over at his place has been proven a difficulty because he lives about 85 min away (with train and bus) and because my mother is so over-protective she doesn't let me take the train later than 6-7, so I can really never see him as much as I want, also it does cost a great deal of money for about 5-6 hours of seeing each other.

Also I'm Swedish and most parents here find it more than okay that young couples get to spend the night together and have sex. My mothers view is more that she would prefer that I date different guys and have coffee with them sometime on the weekend and never do more than kiss. I know that my mother  is concerned because she loves me and does not want me to get in a situation where I would regret myself later (having a bad serious relationship, getting preggers etc). Although my relationship with my boyfriend is already serious, I fucking love him and he's my bestfriend. 

This also comes to the other point. My mother forbid me from having sex and would probably be furious with me if she knew that I was already sexually active with my boyfriend of 8 months. Although we both practice safe sex and are in a loving relationship. 

So reddit! How do I ask my parents for permission to sleep over at my boyfriends? 
How do I make up my argument in a mature manner? Should I mention that we are both having sexual intercourse, or leave that out of the conversation? 
I just want her to realize that I am able to make my own decisions regarding my personal life and that she cannot decide against my own will how serious I should be in a relationship.
<bot>: 18 year old Swedish girl wants to be able to sleep over at her boyfriends. Over-protective mother won't let her. How do?