Metformin and Muscle Pain

I just started taking Metformin for PCOS and suddenly I began having severe muscle pain on my left side, upper thigh area. So severe that I can hardly walk, sit on a chair or get up once I do. I have had no problem with mobility previous to this. I had severe, runny, almost water-like bowel movements so I decreased and then gradually increased the dosage over time which helped resolve this (sorry to be so graphic). I describe the pain like a pulled groin muscle, although I've never experienced that, but that is the area that the pain is in. Has anyone else experienced this type of muscle pain??? If so, what helped if anything?