Can't sync iTunes on iPhone with home windows pc.

It was working fine but now it's not. When I plug in my iPhone 6+ it should say trust this computer but it doesn't, it lights up and says charging. When I go into iTunes on computer it should show my phone in the column on the left but it doesn't. Also I can't get out of iTunes on pc. Normally I click the x in the upper right corner and that closes the program but it doesn't, instead the computer freezes up. The only way to exit iTunes is to shut down computer. I tried uninstalling iTunes then reinstalling it but that didn't help. It's the same. iTunes is also super slow now. Other than iTunes everything else on the computer is working perfectly.