What Is The Cause And Treatment For Recurrent Chest Infection In A Child?

my daughter is 13 years old and has had multiple chest infections over the last months. she has also had trouble breathing. she gets constipated then out of the blue has diharrea and then the cycle keeps going. also she always seems to have a lot of mucus to cough up. i am not a doctor but could this be late onset of cystic fibrosis?