Flying away from the nest...

I live with my mom and my two little brothers and I am currently 18. My boyfriend is 22. We havent been dating very long but my family is always in the way and I cant get to really be with my man. We would like to move in together into our own place. Tough sitch is my mom can't let me go. I don't want to hurt her, but I need to leave. What should I do? Should I just leave or stay and be miserable and lose out on my relationship? Please help.