Persistent leg pain

[Amberreyes95]

Hello,  
I am a 20 year old female. I would consider myself pretty healthy and active since I was kid but I have had a persistent  leg pain issue since I was kid.  For as long as I could remember I would have very strong leg pains occasionally during the night.  The pain would either wake me up at night or it wouldn't let me go to sleep. Since I was younger,  the doctor said it was growing pains but considering I'm 20 and I haven't grown an inch since 5th grade I sincerely doubt that. The pain happens usually once or twice a month still to this day.  It is really bad and there's nothing that helps expect putting my leg directly in front of a heater and taking medication.  I have gone  back to the doctor and they checked for chemical imbalance such as my potassium levels  but they came back normal.  I've noticed that when the pain sets in my legs are colder than usual and my knee begins to make popping noises every time I bend it. The pain basically feels like I've been hit by a car on that side and it's been shattered.  Im tired of taking medication every month and I don't think it's normal but the doctors have yet to give me an explanation.  Does anyone  have an idea?