metformin and PCOS

So, my primary care Dr brought up putting me on Metformin because I have been to the ER 3 times in the past year and all 3 times my blood sugar was raging! but she checked just at a regular appointment and it was fine so I am worried that if she puts me on Metformin if will make me sick if nothing is wrong with me. I do have PCOS so that's why she figured I would need metformin, do any of you ladies have any advice? Did you guys get pregnant successfully on Metformin? I'm just worried about blood sugar medicine if I don't particularly need it. We have been TTC for 74 months with no luck, very irregular periods