I was in a rut with my hair like you are, as I began straightening it in middle school. I had absolutely NOOO idea how to care for my curly hair at all, and I've even tried stopping washing it altogether. I had definite heat damage and random straight pieces in it. I used to spray hairspray on my hair before I straightened it to make it stay straight. I don't do the no-poo method as products (even if they're CG) and my natural oils like to build up on my hair. I just wash with shampoo and conditioner 2-3 times a week.
Anywho, stopping dying your hair is good as it will cut down on the damage. You don't have to stop altogether, just be more gentle with your hair. I've seen some girls with wonderfully healthy dyed curls. Your hair won't necessarily fall out if you continue to style it with heat, but it will continue to break. Invest in protective styles on days you don't want to straighten your hair such as braids, cute updos, whatever you like
Also, use styling products such as mousses, gels, etc. if you would like nice defined waves/curls and minimal frizz.
Leave-in conditioners also provide a nice amount of moisture to damaged hair, and cut down on that yucky damaged feeling. It will take some trial and error to find products you like. However, the only real way to get rid of damage is to cut it off. But if you take care of your hair, you can slowly grow it out.
I'm sure your hair texture has loosened due to genetics (quite possibly puberty) and most likely heat damage. My hair's curl tightened up as I got older. No-one's hair completely fits into a hair type. I have nearly straight pieces on certain parts of my head, and really tight ringlets especially around my face and my temples. If i were to completely describe all of my hair types, it would range from 2a-3b. Crazy, I know. And I have crazy thick, frizzy, tailbone length hair.
If you would like to keep straightening your hair, try and stretch out the straight style. Try wrapping your hair up at night and putting shine serums in it. Do not wash and straighten every day. Try to use as minimal heat as possible in order to keep your hair healthy.
Geez I wrote so much :x I hope this helps!