I don't know if I believe in God, and I am not silly. (Well, sometimes, I am, but I think God will forgive me. :P) There's no way to prove God, and I think that not knowing is half the fun.
When I was a Christian, I had these "experiences of God" in the past. But it could have just been nice music and community making me feel really happy. Regardless of who you are, and even if you have great faith, you can never be sure at all times.
I know any person who believes they have the one (capital t) Truth will disagree, but after studying religion for years (although there is much more to know), I feel that if there is an omnipotent, benevolent God like many think, he/she/it would know that nothing is black and white. As Catherine the Great said, "The more a man knows, the more he forgives." If God knows EVERYTHING then he (or whatever pronoun you can correctly attribute to God) has got to be really forgiving...even if we aren't whatever religion people claim is correct. No one can claim that God actually called them up and told them, "___ religion is true. So, if no one has any advantage over the rest of us (such as receiving phone calls from God), each religion is just an idea, one that is a human creation. I don't think that is necessarily bad, however. Religion is very important. It is just when it is oppressive and becomes part of the state that it is dangerous.
Even though I am not sure, I still pray once and a while. Maybe it is because I got used to it as a Christian, but it is my way of connecting myself to the universe and my idea of God, even if it is wavering and unsteady.
When I decided that I was going to question Christianity (and all religion, for that matter), I prayed to God and asked that he/she would lead me to where he/she wants me to be. I was deeply committed to following God's commands, and I still believe that if there is a God out there, I did follow what he/she wants.
I stopped being a Christian when I started being honest with myself, and admitted that I can't know, and I can't make all these claims about the universe because it is a lie to say I know. Don't get me wrong, I don't want to insult any religious people out there...but this was my experience.
I think that anyone who believes they can prove that God exists is afraid and trying too hard. Its impossible, so relax.