Since starting Metformin back in 2020 my periods have been VERY predictable, along with positive OPKs mid-month but no pregnancies(PCOS & Endo). The first day of my last period was August 31st. (I had taken a pregnancy test before that day NEGATIVE). For the first time in over a year, I didn't get a positive OPK in September also my period was expected September 30th. I took a pregnancy test October 2nd and another test on the 7th. Still negative. YOUR THOUGHTS?? I'm still taking Metformin 750mg. No abnormal symptoms, I just really felt like I was going to start my period last week: cramps, sore breasts, but it never started. Those symptoms have subsided. Still testing negative and Period is now 8 days late.