I can't read my messages on iPhone?

I'm getting my messages and you can see that I've received them in my notification bar and the message icon has the number 3 on it in the home screen but when I go on messages the messages aren't there and some of my old messages have been deleted.
I don't know what to do?

If old messages are being deleted your phone is probably trying to make room for new messages. Delete old messages and then restart your phone by holding down the button on the top of your phone. If that doesn't work call Apple. 866-618-4787