Thanks for helping me out, Bosanbo. I was thinking about the effect this length could have on my hair. But the shortest part of my hair isn't shorter then on my last haircut, it is only more hair that is cut shorter now.

I think it is more like something is coating my hair and prevent it from absorbing moisture and/or product. The hairs on top of my head felt and sounded squeaking clean.. So I put my hair to the test and this evening I misted my hair with my water/lavender oil mixture only on the straighter parts near the roots and immediately they started to curl!
So, although I can't explain how it is possible to overprotein my hair and still have my hair looking healthy shining, but straight, this is my theory:
I've clarified my hair with SLES poo, not much later used Kesham (this works like PT for me) to cleans my hair and add protein. But the more I did, the straighter my hair got especially on top of my head. Like nothing of my styling products got through.. so I figured, if protein fills the gaps of your hair, once you do with low porous hair, your hair will shine and bounce back. Except, when you overdo it. Your hair might get weight down and doesn't allow any moisture or product in to let it do its job. I think that is the case with my hair. I don't need more protein, but more moisture. The protein works like a barrier on my low porosity hair and weighs it down somehow. Does this make sense?

2b-c/3a med/fine- low porosity- normal elasticity, BSL
2B/C-3A) fine - low porosity
Wash: Daily Fix,SMT, Kesham, Urtekram
RO: Motions CPR Li, Inecto Cocos co, AO GPB, KCTT
acv-rinse, sometimes honey-rinse
LI: coconut oil (winter), CJBC-LI
Styling: AVG, Etos Solid Power Gel, Taft gel, CJPP
Plopping~Pixiecurl diffuse~clipping