I had a very similar experience with my third flush. I woke up in the middle of the night in horrible pain. I drank a second dose of oo and grapefruit and a little more epsom. It didn't completely make it go away but it helped. I am pretty sure that my problem was a stone stuck in a duct. More es to dilate the bile duct and more oo to lubricate and help it slip through seemed to do the trick.
As far as future flushes- I was terrified. What I have done since though with no problems is up the oo from 1/2 to 3/4 of a cup. I have no pain with flushes or right after since.