Toilets, Sinks, Showers, Tubs and Disposals - Shower scalding HOT or freezing COLD

We installed a price pfister tub/shower faucet about 2 years ago. When first installed, it worked just fine. We stopped using the bathroom during a lengthy remodel and about three weeks ago started using again. When I first started using it, there was hardly any hot water then, it seemed to "kick" in after several showers. Now, the cold water hardly works and when I try to shower it's either HOT or COLD. I can hear an dull thud when the mixer (?) changes from hot to cold. Also, I have to open and close the valve several times to get the cold to engage at all. This is a singe handle tub/shower faucet. Any help is greatly appreciated... I would like this remodel to end sometime soon!!

If you have done a remodel, you have stirred up crud in your system. My bet is you have some of this crud in your valve. You will have to turn off the water to the house and remove the cartridge to check for and clean the crud out.