Now we've clarified that you're talking about God, the Christian God, then no. You're a Christian. You don't need to specify which denomination you are, because you're part of the larger superset of Christianity.
Oh, you could be a Satanist, but that's merely a form of Christianity, to be honest. And before I get flamed for that, to be a Satanist, you need to buy into the whole god/satan dichotomy that's a major part of Christianity. Satan is only the bad guy in Christianity, so Satanism wouldn't exist without Christianity. You need to first believe in God before you can believe in Satan. Doing so makes you basically Christian.