Does Metformin Cause Weight Gain?

My mom said the first week or two she had stomach issues, after that her body got used to it. If you have been on it for longer than that, maybe you could ask for a lower dose? My experience has been weight loss. But I also have a question about metformin... has anyone experienced continued upset stomach and diarhrrea when taking it? I am on mg a day and my poor stomach is always upset. I'm on vacation now, but can't imagine what it will be like to feel this way all of the time when school is back in session...I just can't go running out of the classroom to the potty all the time!