Since sunday I'm having a series of strange bad hairdays...

Whenever I wet my hair, it turns out like a bird's nest at the back!
What I do: I wet my hair upside down, use YTC (which I used before), then scrunch in mousse or gel, then diffuse
What happens: when I'm back upright, the back of my hair is parted in 2 and the back seems way shorter than the front it seems like the down layers want to go to my canopy if that makes sense. I do not have more curl than usual, so it isn't more shrinkage... just a mess...so I have to get my hair soaked again like 5 times before it turns out ok-ish
What has changed:
- sunday (the day my problem started) it got warmer, with dews in the 40-50 range (before they were in the 30s)
- I dyed my hair on friday, but rewetted on friday and saturday and then it was still ok (even nice on saturday)

What could be causing my problem? and does anyone else have this problem? And what should I do now?