My Mum won't let me break up with him...:(?

I went out on a first date last week with a guy who turned out to be an absolute creep. He was touching and me everywhere, trying to force his tongue in my mouth, telling me he loved me and that he wanted to be my first time! I told him no and that I was so uncomfortable, and left. I told my Mum when I got home and she just laughed and told me that's what all guys are like, he kept sending me messages and when I blocked him my Mum got mad and made me re-add him and send him an apology message or else I was grounded. She always answers his calls and tells me that I'm rude for saying no when he tells me I'm a princess and that he loves me. I completely hate him and I'm afraid to be around him, he's asked me out again and my Mum says that I'm grounded for the summer if I don't go, what can I do?! :(