incontinence

I have been using an Hitachi Magic Wand for a number of months now with no problem reaching an orgasm within the first few minutes without anything out of the ordinary happening. However, the past two times, during orgasm (clitoral) for what I thought was ejaculation turned out to be urine. I thought the first time was ejaculation as there was no odor but once dried, it was yellow so I had my doubts. Today, I knew it was urine from the smell. I was so disappointed as I had surgery a year ago to stop my incontenance problem and now I think it has come back. I can't remember what the surgery was exactly but part of it involved insertion of a sling I think. Is the wand too powerful for me? Why am I urinating all of a sudden? Has this happened to other women?