What Is The Cause And Treatment For Inflated Hip Flexors?

Hi Doctor. I am 13 years old. I do track and i keep on getting my hip flexors inflated. i have went to a doctor 3-4 times an they tell me the same things, Take Ibroprofen, do extra stretches, and put on heat pads. And i keep on getting inflated hip flexors back. Can you tell me what to do? like what stretches Etc.