Curly haired women

How do you get your hair to curl at the top? My hair is curly naturally but it's also thin so when it's a bit longer, the weight of my hair makes it flat on the top and it only starts curling halfway down my head. When I cut my hair short it curls all the way but I don't want short hair, I want long curly hair.

I use a hyaluronic conditioner, a fine hair friendly shampoo, I use a leave in conditioner spray (so it's not heavy) and then I wrap it all up in a tshirt to dry but it's still flat on top.

What am I doing wrong?