What Causes Flank Pain In 13 Years Old?

my 13 yr old daughter has been complaining about flank pain in both sides as well as it hurting when she breathes and in general not feeling well. No fever, No cough or sickness. Took her to pediatrician on monday thinking she might have a bladder infection or kidney infection but urinalysis was normal. She does have mild excercise induced asthma but inhaler does not seem to make her feel better either and she is not wheezing or coughing or anything.