An odd thing happenned....

Dear Dr. Vinograd,
I'm just curious over something that I experiencced last night. I have been using one pad a night and I alternate feet every night. Last night it was my left foot. I had placed the pad higher up this time, covering most of the ball of the foot in order to cover more reflexology points.
In the middle of the night I was awakened by a sharp, needle-like pain on my left foot. I had had for a while, and then I began to feel a much fainter pain on the right foot, at the identical location. The faint pain disappeared as quickly as it began, the sharper left foot pain persisted for a while and then left also. However a little while later there was a dull, slightly burning pain all over where the whole pad was located.
It was obvious to me that the cause was the result of the pad working, but what exactly could this have been? In the morning I checked a reflexology chart and the point affected was the stomach or intestines.
I have used the pads for a little over a week now and in the morning they are beginning to appear slightly lighter. I am saving them all in order so I can later look at them again for comparison.
Thank you very much.
ALi