iMessages not working properly since iOS 7.1?

Ever since updating my iPhone 5S to iOS 7.1, my iMessages have been playing up. I will send a message to someone and 5 minutes later it will tell me that it didn't send, but the person gets my message anyway. And I will not recieve messages until hours after they have been sent. Very annoying please tell me how to resolve this problem!! I have tried turning it off and back on again, no change.