I think this is typical for liver flush. It can happen, especially when you still have food in the small intestine.
Out of 20+ flush I have done so far, about 5 flush gave me the symptoms you described, especailly more so when I ate something at dinner time prior to the flush.
What happen is the oil content you drank can't go down the digestive track and it is trying to going back out from your stomach, which gave you that horrible sensation.
I fix this problem by getting a hair dryer and blow warm heat at my abdomen, and at the same time message my abdomen in a fast circular motion. If it didn't work, I will then go chew some ginger or eat some hot pepper with noodle soup (must be hot and spicy) to push the oil content back down. This should work most of the time.
Except for one time, I tried all but it didn't work, so I ended up throwing up, but that's the way it is-I said to myself.