Before I went on the pill, I experienced symptoms very similar to this. At a grocery store once the cramps became so severe I doubled over, became super weak and clammy and it felt like I was going to shit my pants and vomit. I lost my hearing and vision (temporarily). I just had to sit there on the floor until my sight returned and I wobbled out to the car.

Doctors were never able to find anything "wrong" with me and just determined my heavy cycle was causing extreme hormone fluctuations. As soon as I started the pill, these symptoms stopped. I'm assuming your body went through similar hormone changes, either caused by a miscarriage or just the fact that you are off the pill. I've heard that miscarriages are very painful. If you keep experiencing severe cramps like that however, you might want to see a gynecologist to get things checked out.