My phone can receive texts.. but wont tell me when they come in, or pop up in my screen like before

[AC Question]

See, I started to notice one day when a friend sent me a message that my message notification wasn't going off, and when I did check my messages, there was a message from her. I turned off my phone thinking that it might have been a minor glitch, so I wasn't worried. But the next day i had about 14 unread messages after getting out of class but my phone had never notified me on the home screen nor had there been anything on the notification bar. I haven't touched any settings either. How do I fix this???