PLEASE HELP. Family drama.

My parents are very strict and make it difficult for me to do what makes me happy (they constantly pull the "you're under our roof" line). If I stay the night at my boyfriends anymore than once a week I get in massive trouble and then am on the outs with my family. There's always something I'm doing wrong my with them... First I'm not spending enough time at home so I start sprnding more time at home, then they say I'm not helping enough around the house so I start helping and th n they accuse me of doing absolutely nothing to help and "treating the house like a hotel". There is no talking to my father because he just get angry and yells and something threatens or gets a little violent. All in all, they make me feel miserable all the time and like I'm not good enough. 

I want to move out and in with my boyfriend and his mother until we finish Uni next year, but in previous conversation with my parents on doing that they said they will not support it as they see it as wanting to change families and they would be very disappointed. I want to just do it anyway, because I know that I would be so much happier but I am afraid of losing my family in the process. But I just can't take it anymore especially when iv been diagnosed with mild stress/anxiety/depression stemming from this.

What should I do?