What Causes Diarrhea While On Metformin?

Hi, My Ob/gyn had me on Metformin to regulate my periods. I was taking it for about 4 months. For a while, I was having runny stools every day, but I managed to control that with fiber powder. In the 4th month of taking it, I started getting chest pains and pain higher up in my stomach. It seemed to happen about 30 min to an hour after eating certain foods or after taking the meds. So I stopped taking them, but I was still having chest pains after eating those particular foods. Finally, the pains became minimal. I try to eat healthy, but sometimes (and this is not often) I will have a little snack that isn t healthy. I was making a recipe and it called for popcorn. I had ate maybe 5 kernels, and then the chest and stomach pains started again. I ve never had this issue before, and I plan on seeing the doctor for it. I am just in so much pain right now, and I m not sure what to do to alleviate this.