My mother is the exact same, Christian parents can be far to controlling and strict, and there's not really much you can do when you're living with them, because they can really see your every move and know exactly what you're doing.

It's a horrible situation to be in, but just don't tell them anything else, I've refused to admit any kind of sexual behavior to this day... it all depends on what your mother is like though, because I know if I sat down and talked to mine about things she'd just be even angrier lol

Like a lot of other people have said, the best thing to do is probably just to move out.
Start saving up and leave home asap, that way things can sort themselves out... otherwise you're relationship with your parents will just get worse and worse, whereas if you're not there the entire time things should even out a little bit - and you can live your own life more