Please help! So many days of spotting

Sumaya

I have PCOS and trying to conceive.For everyone who has PCOS, dont usually have periods.For me its the opposite.I have spotting for 4-5 days every 14-18 days which leads to a 2-3 day flow. Then goes again to 3-4 days of spotting. Really frustrated and no doctor seem to find what is wrong. Currently on Metformin for five months. Any help will really appreciated. I feel really broken everytime the spotting starts.