I have been through this many times. I had long 4b hair to my shoulder blades and ruined it by getting it pressed the wrong way. Once they go straight, they won't revert to curly again. You probably have stringy parts, this lady thought I was lying when I told her I didn't have a relaxer. I suggest trimming the ends every 3 months. Don't let someone give you the big chop. Deep condition every week for a month, then every 2 weeks for 2 months with a heating cap for min. 20 min but longer if you can 30min - 1hr. I know hair grows back but I didn't want to get it all cut off, so my stylist suggested this regimen. It made my hair healthier at the roots.
4b is me