painful poop peristalsis

Hi there. I am really excited about my new mooncup. I bought a size A because I have two little girls. I had no problem inserting it on the first try yesterday. I am getting the hang of taking it out without making a huge mess. My problem is that it seems to be interfering with my intestine/rectal function. I have very regular (fairly large) bowel movements due to a diet high in fiber. I generally have no problem whatsoever passing my poop, but the cup seems to get in the way of the poop moving into position and leaving my body. I experienced several bouts of painful cramping when my body tried to move my poop along (for non bio geeks, that's the peristalsis part) with the cup in place. I finally pooped this morning, but only after an extremely painful cramp made me take the cup out. Passing the poop was as effortless as usual once the cup was out.

I think the cup is in the right place...it has a great seal and is lower in my vagina than a tampon would be. I can easily reach the sides of the cup and with some effort, can even reach the very top. I tried placing it even lower (just barely inside the vagina), but it leaked a little and I still had the cramping.

I feel great now that I pooped...no cramps at all. I love the cup so much, I want to try to find ways to work around this problem. Any advice you can give would be greatly appreciated.

One thing I would particularly appreciate info about is the size of my cup. Has anyone out there with kids found that the smaller cup was a better fit? Even though I have had children, my vagina has good muscle tone. Do you think maybe I need the smaller size?

Thanks so much for reading this. I look forward to hearing from other cup users sometime soon!