Temp spike after missed period??

So this has never happened. Usually when my temp starts dropping, I’ll get my period. But no period, spotting, cramping or anything. I had some mood swings and fatigue but that’s it. Then my temp started rising again?! I’ve taken several tests and they are negative. Anyone know why my temp would start rising so much after it dropped so late in my cycle? (I use Ava to track my cycles)

UPDATE:

Fertility friend chart (glow won’t let me post the temps cause they’re too low d/t being skin temps)

This is saying I just ovulated day 39. Does it also seem like I ovulated around day 12/13? I do like this graph better than Ava- thanks for the suggestion!