What Causes Diarrhea While On Metformin?

I take metformin for diabetes. since doing that I experience some diarrhea but am having strange, more frequent stomach problems. 3 times now in the last 5 days I have had severe stomach / intestinal CRAMPS for hours, and then comes the diarrhea. I also get throbbing gums, red flushed hot face, and much saliva production. the diarrhea is very watery after a while, after starting out more or less solid. I try sometimes to vomit, but cannot as I had hiatal hernia surgery in 2009 and the new stomach valve is so perfect that it will not allow me to vomit anything at all. Going back to the intestinal cramps----have never had these----but they are very debilitating !! Have not changed my diabetic diet or other activities. have a call in to 2 separate Docs at this time........waiting to hear !! thanx, RLT