New boyfriend

Annalise
I'm 16 and I recently got my first real boyfriend but I don't know when to tell my parents. My mum is really religious and is quite controlling when it comes to me and my friends. She would freak out if she knew I had a boyfriend and would probably think that we were always having sex. When is the right time to tell her without her banning me from seeing him? 
Also: how do I tell her? I've never had to do this before!!