So I've started metformin 1000mg a day on June 6 which was cycle day 1. Before then my periods were irregular and my cycles would last 35-50 days long. I took an ovulation test June 21 and it was positive then I came on my period July 6.. Which I'm assuming the metformin regulated my period  since it never came on time like that before ... Here it aug 11 cycle day 37. Basically I'm 9 days late for AF and getting negative preg test . Could it be that body is changing back irregular :(. I haven't stopped taking metformin so I'm just confused on what's happening !