Doing a protein treatment and following with a deep treament may help with getting some curl back, in the mean time you might try finding some small spongy curlers, that are comfortable to sleep on, or use cut up rags and wrap the straight pieces around the curler or rag while their slightly damp and sleep on them that way as apposed to curling them. I've found putting curlers in when the hair is damp works a lot better than a curling iron when it's dry, and it's a lot less damaging.

Hope that helps some.