Is it OK to hide that I don't believe in a religion?

I have recently accepted that I have no interest in any religious believe, with that I am afraid of telling anyone. I am surrounded with 95% of my peers are either of Christian or 7 days belief, coming out would be very hard because most of them are fundamentalist and I'm afraid I would be shun aside because of my lack of faith. I wanted to know, should I tell them and take a risk of being ostracized or should I just keep it to my self and pretend to have these believes, like going to church, celebrating Christmas etc.