Irritating pain. I am in a problem.

Hi, i am 18 years old female.... I have severe upper upper thighs pain. Its ok when i am sitting or standing still. But when i try to stand up it pains severly in both of the upper thighs. It pains when i get a jerk or somebody pushes me. After such a situation i cant even stand properly for an hour. Now i cant even run or walk faster. I cant even walk properly. I always walk slowly I always feel like crying due to it. As it is an unusual sort of pain..... A kind of irritation. I dont know what happened to me...... I never got an injury. Never even fell down. ( so cant be the reason ) I just got this problem months back . As during my 12th exams i always sit on my bed. Almost the whole day. Didn't even stepped out of my house. This went on for around 2-3 months. I dont know whether this can be the reason.... Please reply me as i seriously need help ..... Plz plz plz reply I am in a problem.