Well, I had one like that. Elle didn't have much hair at all until she was a few weeks old. You said she is weak? Can she nurse? You may have to help her by holding her head up to nurse. I had to do that with Elle. If she starts to roll, as in barrell rolling, you need to get to the vet. Ask your vet about the possibility of a Vestibular Disease. That is a disease that effects the equilibrium. Elle now walks with her head crooked. The sooner you get it, the better, so if she begins to roll, tilts her head, or seems unbalanced/lost all the time, you need to get vet attention. Good luck with your kitties!!!