I'm 4 months postpartum , My cycle is all screwed up and have missed it this month. Just wondering…

I'm 4 months postpartum , My cycle is all screwed up and have missed it this month. Just wondering when other moms it back to a regular menstrual cycle ? Or when did it finally come back. I'm not breast feeding and I've taken a test that was negative. So I'm not really sure why I've missed it. Only thing I could think is that I don't take my BC at the same time every day like I should. (But I still take it)... I'm freaking out so that could also be a factor but I just need other opinions