I suggest you get an anatomy book, as the gall bladder is off to the SIDE of the biliary duct, from the liver to the pancrease/small intestine at the duct of vater.
Your gall bladder will shrink (contract) when the stomach gives the signal that fat has been ingested. Your liver also contracts (hence the stones coming out) with this same stomach signal.
The gall bladdre usually will not try to re-fill until about 1 1/2 hours after a fatty meal has been entered into the stomach.
The act of filling into the gall bladder is a slight pull. If stones are present in the common bile duct, most should just go on their merry way down into the small intestine.
The pain you feel could be from a condition called "sludge" build up on the inside walls of the gall bladder. Surgeons have noticed it on the ones taken out and cut open. The sludge is very thick and gooey. Tissue behind this goo is tender. exposing it to more bile (a base) could be causing the pain, since it hasn't been exposed to bile in a while.
There are posts on some forum here that have patients describing the intense pain of a gall bladder attack after surgeons have removed it. So pain, or no pain, you are doing a good thing for your body by flushing.