Sounds like you might need DFU mode in order to reinstall your OS. This is a more robust procedure. It can be a LITTLE tricky here's a blog that explains how to get your device in to DFU mode.
How to put your iPhone or iPad into DFU mode | iMore
Once that is done, you THEN plug it in to iTunes and let it restore. Your screen on the phone will and should be blank, AND you WILL need to be patient as this takes a while to complete.
WORST case you/ll need to bring it in to Apple for repair, or to an authorized 3rd party iPhone repair shop....
https://support.apple.com/iphone/repair