Hi Tabita,
I'd try the following steps and test the phone after each step:
1/ Clean the screen connector on the board using a cotton swab dipped in 90%+ isopropyl (rubbing) alcohol.
2/ Reset the phone to factory settings. Hope you have a back-up. It is usually done by pressing and holding home button + power button together until the phone restarts (google it). Then choose cache wipe, then choose reset to factory settings.
3/ Dis-assemble the phone and examine the board using a magnifying glass. Look for anything missing/broken/damaged/part removed. If you see anything, take a picture and upload it here. Or if you don't want to do this step, ask a professional to do it for you.
Let us know what you find out.
Good luck.