Why Did I Have Problems Wearing A Menstrual Cup?

I wore a silicone menstrual cup (“Mooncup”) for the first time ever. I had it in for about half an hour with no problems then an area in my lower back began to ache. The pain went down as soon as I took it out but still ached for about 20 minutes.
I put it back in and it hurt again after a while so I had a lie down. But as soon as I tried to lie down, it hurt so much, I thought I was going to faint. So I took it out quickly.
After about 10 minutes in pain I started dry retch... it was exactly like vomiting without all the gunk coming out. It began hurting like crazy, I think around my uterus area. I don’t remember ever feeling so much pain in my life. The pain would rise to an unbearable point then go down to no pain at all for a few seconds, then rise again. This went on for an hour and then finally started to die down over the next few hours.
What happened? Can I still wear the cup? Besides the whole in pain thing, it’s a good invention and I want to be able to wear it!Why Did I Have Problems Wearing A Menstrual Cup?
I have a mooncup, love it and have never experienced anything like this. Have you ever had problems when using tampons? I think you see your doctor as soon as possible just to get checked, this shouldn't happen.
This site has some good info about these products. Be sure to read the info near the bottom for new, first time users. You may need another style or a re-fit. Don't reinsert the thing til you let your doc check you again.
http://en.wikipedia.org/wiki/menstrual_c...