There may be some kind of issue with your touch screen. Let's check the simple stuff first. Try just resetting your phone, press and hold both the Sleep/Wake button and the Home Button for 10-20 seconds until you see the Apple logo. Let go and allow the iPhone to reboot.
Also check to make sure you don't have one of those covers on the screen, sometimes they glitch out the screen. If that doesn't fix the issue, please follow the steps in this article...
http://support.apple.com/kb/ts1827
If nothing changes you'll want to follow these steps to backup your data and call Apple for help in restoring the device or bring into an Apple Store so they can evaluate the device for you there.
http://support.apple.com/kb/HT4137
Out of all my experience with apple devices, this has never occurred. Have you ever dropped your phone or poured any liquid on it?
Hope I helped,
Zack 🙂