I'm not too sure if I can help.
I have PCOS too and I was diagnosed this year. I have been on the contraceptive pill in the past (which stops periods etc), but I found that it never stopped mine. Ever. The first month I used it, I was spotting for 3 or 4 weeks straight before I went back to the health clinic. I can't remember the exact details, but I'm just one of those people that it never stopped my period. I would always spot without fail, no matter the strength of 'the pill'. Therefore, I had to take every pill from the packet and bleed every 28 days. Not that it stopped my pain at all, either.
Perhaps you need to take the placebo pill at the end of this month (if you can wait that long)? It might be a one-off, especially if it hasn't happened before, and things might return to normal next month. Beyond that, I would suggest seeing your gyno