Google play won't stop preparing to download

[AC Question]

When I went to the Google Play Store, everything seemed as usual until I tried to download something. The preparing to download bar (right before the % complete bar) kept going and going and going! (Even overnight!) It has the option to cancel, and I've tried over and over again, and still the same. I've cleared it's cache and force quit it, AND tried to install a different app. Still the same. Please Help Me!!