Metformin 500 mg

So I have PCOS and recently my Ob prescribed Metformin to me and advised that I take them every day for 3-6 months & see if I get pregnant... well I took them for maybe 3 days and couldn't deal with how sick I felt. I started getting dizzy and super nauseous on top of the freaking diarrhea, regardless of whether I ate or not. The crazy thing is I use to take 800mg and never felt as bad as I did this last time with 500mg. Maybe I should cut them in half? I've also been taking another supplement that's seems to have helped my body ovulate so idk if the meds are counter reacting or something... anyone had similar symptoms with Metformin??