Can weaning cause a missed period?

I got my period 6 months postpartum and they've been regular every month. My baby is now a few weeks shy of 1 year. A few weeks ago I started slowly weaning. I was never able to exclusively breastfeed because I didn't produce enough and barely got any milk on my right side. Baby is still nursing the same on left side but we basically stopped on the right (she was mostly just doing it for comfort for months - never got more than half an ounce pumping). 
I'm on day 36 of my cycle and typically have 30 day cycles. Took 2 tests that were negative yesterday. 
Late because of weaning? Or tested too early? 
*use condoms for birth control