longer and longer periods

I've been tracking my cycles for a couple years now and this last year my cycles keep getting longer and longer. 
My average cycle is around 36 days now. But ranges from 28-40... 
I'm starting to worry that I'm no longer ovulating. 😔 which sucks because my husband has finally agreed to have a baby. 
I'm on day 39 of my cycle and no sign of my period but I got a negative pregnancy test
Feeling pretty nervous that I may have missed my window.