iPhone 4s not notifying me of messages until 1hour later

When texting someone my phone won't notify me about it, I click on the conversation to see if I have a new message but there isn't any and then about 1 hour later my phone will light up and make a sound saying I have a message from 1 hour ago . I have the latest iOS7. It has only been happening recently. I hope that there is a way if solving this so I can reply to messages quickly.