Mirena, Irregular Cycle, AF Possibly Late?

QuickSilver
I had my Mirena out on the 20th of September. On the 26th of Sept I started AF and it lasted 13 looooong days. 
Since then I haven't had any sign of AF at all. I've taken a couple of pregnancy tests, both negative (but that was a week ago now). I'm pretty sure, based on bbt and my apps, that ovulated on October 15th. We had sexy times on October 11, 12, 13, and 15.  I took a test on the 25th (so 10 days DPO) and it was negative. Like not even a super faint line. I've been too cheap to test since then LOL. 
I have been kind of nauseated off and on, but none of my other normal pregnancy symptoms are happening (this will be my third baby but my first two are 12 and 14 so it's been a looooong time). 
I think I might break down and test tomorrow because I am on cycle day 36 and that seems crazy.  If it's still negative I don't know how long I should wait until I see my doctor?  If I ovulated and didn't get pregnant my AF should have come by now for sure I would think?  So confusing.