What is going on with my iPhone?

This morning,I was using it, but something wasn't right. I couldn't access the home screen or the "App History" menu. I managed to activate my "Tap Three Times" command to work(Invert Colors), and Siri worked fine. I couldn't make calls or send messages, and all of my other apps other than Facebook, which I was using at the time, wouldn't open. There also seems to be a problem involving the Lock Button. If I press it when the screen is turned on, it closes instantly. However, it does not bring me to the Lock Screen when I press it again, or turn on at all. I can still get Siri to work when the screen is off, though nothing displayed on the screen, and after holding the Power Button for a long time, it brings me back to what the screen looked like when I turned it off. I honestly have no idea what's going on or what I need to do to fix it.