periods after baby

I'm almost 8 months postpartum and my period was on track after little man came usually the 12th of every month for 3 days pretty easy id say .. well this month it just hasn't came, I did take a test about a week after it should have been here and it was negative .. thank goodness! But it's still not here and really showing no signs of it coming anytime soon. I'm usually pretty good at predicting when it's going to start and what not. with my son I never had any signs of being pregnant just thought would take a test as my fiance and I decided to try, I was pregnant within a month of that. so I guess my question really is should I be worried ? should I take another test or wait it out till after the 12 when it's supposed to come ? Sorry it's alot and may be a bit confusing just need some advice without asking family