What's going on with my iPhone?

I left my iPhone plugged into my computer all night, and when I took it out this morning, it wasn’t working. If I hit the home button or the button on the top, the only thing that happens is the screen gets a little lighter. I can’t turn it on or off; I’ll hold the top button and nothing will happen. The volume control on the side still works, and when I hold the home button voice control works, but I can’t do anything else. My computer still recognizes it when I plug it in, but the screen is still dark. I think I just received a text message because it just vibrated and the screen lit up a little, but I can’t turn it on. What should I do?