Told my boyfriend I am a lesbian and im afraid hes gonna tell people?

A few days ago I told my boyfriend im a lesbian, I had been keeping this from him for a while and I NEEDED to tell him fast! When I first started dating him I thought I was bisexual but then I realized...im not. He FLIPPED OUT when I told him! He said I should go join my friends in NY with their parade, he never wants to speak to me again, and he is disgusted. I don't care, he was sexist to me ALL the time anyways. BUT! I am only 16 and I still have to live with my mother, so I am worried of her finding out. She didn't know he was my boyfriend, she just thought he was a friend. (She over reacts to pretty much everything so I don't ever tell her anything about my personal life) Now I haven't talked to him for few days and she has been asking me why. She is going to start wondering more when I don't hang out with him anymore or why I don't text him. What am I supposed to tell her? I can't say I broke up with him because she didn't know we were dating! Help me!!