I'm sorry you're having a hard time. I don't know what you have, but I hope this piece of advice can help:

Instead of co-washing, try using a gentle shampoo (free of sulfates) only on your scalp (leave conditioner on the ends to protect them) rinse, then condition every time you wash your hair.

The Lemon-aid rinse in Curly Girl may be helpful too.

Good luck!
2a/M-C/ii hair. Super long.