due to straightening is a common occurance. if you are seeing broken shafts, means your is also probably dry.
Dryness can be tackled with use of mild shampoo, oiling the hairs before shampooing(so there is less damage to already brittle shaft); and conditioners.
In addition increase the intake of protein, iron, antioxidants
in your diet to improve the new growth.
Taking a hair specific multivitamin
supplement like biotin
will also help you.