Pcos and metformin

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Hi all! I was diagnosed with PCOS last month and have been taking 1000 mg of metformin this month. I have regular 30 day cycles, normal/heavy periods until this month. I “started” my period yesterday but it’s so light that I don’t even need a tampon. It’s more like brown discharge. I was wondering if the Metformin is messing with my period!? Is this normal?