Ugh!!!

According to glow my af wasn't due till the 2nd of July, but I started pinky bleeding yesterday, that went to a sort of reddy when wiping, then brown then stopped altogether and has went back to pink today! Going crazy here ? I feel cramps like af is about to come. I'm on 1000mg of metformin for pcos (always had a period though) and this month my positive opk was cd14 (17th) compared to last month when I was only on 500mg it was cd23 before a positive opk! That's the only difference but af comes 4 days early an acts really strange, past few months I'll be extremely light for a day or two before af but it's always brown blood now I'm totally thrown lol