Hi, metformin is well known to cause upset stomach for some people .
From my personal experience I stuck with it for 6 years but it caused me problems with my tum and constantly running to the loo and it got to the point that it was affecting my life too much.
At the end of June this year I decided enough was enough, stopped the metformin, overhauled my diet to low carb. No more running to the loo, lost 34lbs and feel the best I have in a long while.
Have you tried taking the metformin with food? If you feel you are not tolerating the metformin and things are not getting any better speak to your GP there are other alternatives they can prescribe.
Good luck