I have PCOS and have been on metformin for about a month. I was supposed to get my period somewhere between dec 13 and 19th but it has not come.  I've taken 4 pregnancy tests, all negative.  I called and left a message with my dr with the same question but will not hear back for a few days.  I thought metformin helped regulate it but I'm starting to wonder if I was wrong. Anyone know what the deal could be?