I have a similar "problem" with my hair. In fact, I've kept it short most my adult life to try and not have to worry about it. I Canmore easily straighten it the shorter it is.
I have large S curls with smaller ringlet (think shirly temple) on the lowest nape of my neck. The other hair actually gets curlier the longer it is because the curl has more room to develop. As it gets longer, the hair has a chance to move how it wants. KWIM? I'm a 2c---3a.
Rae ~ 2c/3a ~
Wife to a 3c Curly Guy
Mom to a straight and a curly.

"The Longer the Hair, the Bigger the Blob."

Porous, very dense but fine hair. Medium everything else.
CoWash: Tressemee naturals
RO: Generic biolage and generic joico k-pak
LI: Tresemee
Miss Jessie's Pillow soft curls, diffuse 50%, add KCCC and diffuse to 80%.
Always wash upside down.