Iphone 4 is sending messages that were sent earlier?

I've had this problem before but now it's just getting out of control.
My iPhone 4 is sending messages to people that were previously sent.already
The original texts will go through and I will continue on with conversation but then they'll go through again, sometimes hours later other times days later. It's getting really annoying and it makes me look like a lunatic to the receivers of the texts.
They don't show up on my phone as being sent again.
I don't know what to do, I've tried turning my phone off and on again and deleting my messages.
What should I do!

Added (1). I;m also leaving for basic training (ARMY) in the beginning September, so I would rather have a phone that works so I can contact my family and friends after my graduation from that. Not having to worry about multiple messages being sent and all that. So breaking it wouldn't be a good idea, I'm not stupid. Nor do I find useless comments to be funny.

Drop it in the toilet

You should try to take the battery out for aleast 10 minutes then put it back on. Or you can just get a galaxy I think is way better.