Iphone 4 freezing when turning on at apple logo/?

I have had this particular iphone for just about two months and was a replacement to my previously water damaged phone. It has recently over the past few days started to freeze whenever on twitter and the app always crashes but other than that there are no noticeable flaws with the phone. Earlier on a friend told me i was not receiving my immesages as the had sent me them and i had not received them so i reloaded my phone or reset it or whatever it is called when you press and hold the lock button and home button for ten seconds. It turned back on but froze at the apple logo. I plugged it into my itunes but it did not show up and I don't know what to do, help?

Added (1). No it is not jailbroken

Is it jailbroken?