Is cholecystitis painful?

Yes. Chronic cholecystitis or biliary colic is caused by transient obstruction of the gallbladder by a gallstone, causing fairly classic right-upper or upper-midline pain(non-cramping, severe, radiating into back); the pain is often associated with nausea+/-vomiting and bloating. Acute cholecystitis will cause the same pain, however it may last for a day or more, and may be associated with fever.