Period talk!?

Savannah • Baby girl - Aliviah Mae 10.29.15 & Baby boy- Archer Neil 05.31.17 👨‍👩‍👧‍👦
Hey ladies!!
It has been 52 days since my LMP and all blood and hpt come back negative. I feel pretty pregnant (I already have a six month old) but apparently I'm not? Im not breastfeeding, no birth control and I had 3 consecutive periods after giving birth but just had my last at the end of January. My cycles are usually about 40 days long so maybe that has something to do with it? I'm getting kind of concerned and just wondering what the longest time any of you have went without a period? Btw my periods have been pretty regular since I was about 15 (I'm 21 now). I started when I was 12 and they were slightly irregular for a year or so but I figured that was normal. I'm just wondering if its normal to skip a few periods after being so regular, and I'm confused with what my body is doing right now! Anybody else miss a few periods?!? 🙈