Perhaps you have somehow turned on the Zoom feature of Accessibility? Take a look at the following article and see if it doesn't help you correct the problem.

http://ipad.about.com/od/iPad_Troubleshooting/ss/How-To-Fix-My-iPad-Is-Zoomed-In.htm

Perhaps you have somehow turned on the Zoom feature of Accessibility?

• Open the settings app
• tap general
• tap accessibility
• turn off zoom

If you need more details, the following article might help

https://www.apple.com/ios/accessibility-tips/