My hair gets curly underneath my hair?

PLEASE ANSWER ME!!! My hair gets super curly underneath. When I try to straighten it, it gets dry and never looks straight either. I usually take a shower at night, and my hair is wet when I sleep. I have tried to take a shower in the morning but it still looks the same. The rest of my hair is soft and wavy, but the hair at the nape of my neck is like I described. Olivia.. Merry Christmas!!