Pretty interesting since I had the same problems a decade ago.
At 16, I opened my eyes and found out I couldn't believe all this religious nonsense. I just told my parents I didn't believe these anymore and mass was just a waste of time. Of course my parents went maniac about this, and even threatened me to get me out of school. I began to refuse to go to the mass (as we did every sunday), but they kinda forced me to go at first, then I refused to participate to communion, did not sang anymore, just couldn't do anything than sit without moving. After a while, I just did not got to mass anymore and my parents kinda accepted my refusal of religion. Although, I got definitively out of my parents house for my studies, and finally my relationship with my parents got really better.
I also did something at that time, that may have helped things a lot : I went to see a local priest and told him the whole story. I don't know if it helped, or if he talked to my parents, it just helped me to talk about this to someone. Even if religions disgusts me in general, I've to say that I've met a lot of priests who were really fine, understanding persons. This may help you, to see the local priest for mediation between you and your parents.
Good luck, you'll need some.
Edit : yes Wiccan ? ^^ sorry, I had to make that joke :D :goes to bed:
