I feel guilty after having sex?

I'm 15 and I just lost my virginity to someone I love so much. He was a virgin too and he's 17. I live in a Christian household and my parents and grandparents are very Christian. I believe I am Christian too but I don't see anything wrong with having sex with this boy. I don't feel guilty about what God thinks of me. Just what my parents would think of me if they knew. I kind of feel like I've let them down and they don't even know I've had sex. What can I do to shake this guilt?