Hi welcome to HCM Dear I can understand your concern for your short heght . You should not worry about it . Some people grow slowly & gragualy ,some may pick up very fast . Being at 15 your height 5 4 is not bad . You should not worry about it . Still you have time to grow .Ht. increases till the age of 22 . It is right time to feel cocerned about your Ht .Going to gym regularly helps a lot if you have strong immune system ,by caring for your life style and food habits along with regular exercises , specially,in fact , all stretching exercises , if done under proper guidance .Also walk, Yoga , Dhanurassan, Taddasan , Chakkarasn ,Bhujjangasan , ,Pranayam , Kapalbhatti ,Deep Breathing and Meditation , help to strengthen your immune system . Include essential nutrients in your diet --FIBER RICH , LOW SALT - DIET ,fruit , veges , vitamins and minerals in natural form -, coconut water , , nuts , almonds , and supplements full of antioxidants as Lemon , Aloe vera juice + Amla butter ,milk ,cheese is very important for our sound mental and physical health and strengthen immune response naturally and help achieve your dream . Hope this helps solves your query .Take care .All the best . Don t hesitate to get back in case of any further query