What do I do about my parents and my boyfriend?

My parents dont want me dating him cus he's not a Christian. But I'm dating him anyway. We've been going out for a little over 5 months now and I'm in love with him. But this whole secret is driving me nuts. I want to wait until I'm over 18 to tell them (I'm 17 I'll be 18 in 8 months) but i just don't know what to do anymore. If I keep it a secret for a while longer (say another year or so) theyll be pissed I didn't listen to them and hurt. But if I tell them now theyll be pissed and hurt and they will try to stop me from being with him. I dont know what to do. I feel like one way I lose a very special boy and the other I greatly hurt the little of a relationship i have with my parents....it's starting to kill me inside but I desperately don't want to lose him....what do I do???? What's the best thing I could do right know. Btw my mom doesnt now how to let go and let me grow up. She treats me like I can't make my own decisions and my whole life is hers. And I dont have the guts to stand up to her...that's how I got in this mess....please help me...