Not religious... do you believe in God?

The reason I am asking is because, well, I am not religious. I mean, I know the gist of some religions such as Christianity and Catholicism (sp?) etc. My Dad is Catholic and used to go to church. I went to church as a young child but don't remember. I grew up with no real religious influence. However, I do believe in God, to an extent. I'm not a full on believer, but i like to think that there is a God. if someone asks me why I am believe in God, I don't know what to say. What would be my reasoning, I don't even know!!! It's so confusing. So, to people who are more in the same boat as me ie not completely religious but believe in God. Why do you?