Metformin has some pretty hard to handle side effects. I don't know what dose you are on but my guess is that the doctor just wanted to start you off at a lower dose to get your body used to it.
I've had my dosage changed many many times, because it has had some very rough side effects on me. I'm actually now taking the extended release metformin which is so much better for me. But it has taken me 4 years to get to this point!
Anyway, don't take it hard if your meds are increased. You need the right dosage to keep from getting other diabetes related illnesses.
You are doing the right thing, dieting and exercise. You will get there.
*Take pride in how far you have come and have faith in how far you can go!*
"Failures are made only by those who fail to dare, not by those who dare to fail." ~ Lester B. Pearson