Doctors always say to have a healthy and balanced diet but what is a healthy balanced diet what kind of foods should i eat am 98 pounds and 5'4 ?

Eat more protein: 98 pounds is a little too slim for 5'4", even for a teenager. Make sure you are getting in 60 grams or more of complete protein (animal source or from soybeans), lots of fresh vegetables and fruits, and avoid foods without nutritional value (like candy, snack foods, white bread). Always eat your protein first if you get full early.