How are you taking your meformin?
For the first year or so I was on 4 x500 every day two at night two in the morning and I found I had to actually take it during a meal, even 5 mins before would cause a problem, and even right after didn't seem to work.
I have since been reduced to 1 at night and one in the morning and don't have quite the same problems with the reduced dose.
If you really cannot tolerate it then you should go and ask for the slow release version, they may not give it toyou unlessyou ask as it is dearer.