Am I disrespectful to the Catholic church because of this?

I was Catholic from birth because my parents are Catholic. I've been baptized, I've had my First Communion, and I've gone through the whole Catholic shebang. But recently, I've decided to dig deeper because I've been feeling distant from religious matters. I respect people who believe in their own gods, but personally, I don't really care whether God exists or not. If He does, then good for the people who have faith in Him. I just don't care much about religion, and because of that, I consider myself an apathetic agnostic. That said, I still do the Sign of the Cross out of habit sometimes, forgetting that I'm an apathetic agnostic. Lately, though, I've been feeling down and guilty about it. I feel like I've failed God by being an apathetic agnostic instead of remaining Catholic. Even so, I still participate in religious activities out of respect, and because they're required by my school. Now I want to ask this to Catholics, since I'll be going back to school next month and I don't want to look like a headless chicken who doesn't know what to do as an apathetic agnostic. If it's time for Communion and I'm in line because I haven't told anybody—not even my parents—that I'm an apathetic agnostic, I shouldn't receive the Host, right? If so, what should I do instead?