Negative Pregnancy Tests But No Period

I should have started on October 1st but nothing ever happened. I'm 11 months postpartum and have had 2 cycles after giving birth. My first cycle was in July; it was a 38 day cycle. I also had one in August, 38 day cycle as well. Now my period has disappeared! Why would I have 2 cycles then just stop. I've taken pregnancy tests but all are negative. I have also taken OPKS and have had a lot of positives. I'm just not understanding. Before my 2 previous cycles I'd have spotting or blood streaks in cm but notta!! Please if anyone has any insight I'd appreciate it! Btw I'm not breastfeeding anymore. Thank you!