After many years of straightening, it's likely dry and damaged. Been there, done that! Your hair needs moisture and some TLC. You won't see the full potential of your curls until you get back in good condition. It can take some time to find the right products for your hair but you've taken an important first step by stopping the damage from the flat iron. Be patient, read, experiment and read some more. You'll find some great info on products, techniques and styling tips here.
3B, fine, normal to low porosity
Modified CG since June 2010
HGs: FSG, anything with glycerin, Tresemme Naturals conditioner, Curls Like Us cloths, satin pillowcases.