What Could These Symptoms Be?

Hi. I'm an 18 year old female. I've had this sharp pain in my thigh. I don't know what it could be due to. I didnt pull a muscle and I haven't tore anythig. I don't play sports or exercise. It hurts when I walk, like when I step with that leg and sometimes even when I'm just sitting. This started many a month ago, happened for a few days, went away, and now it's back. I don't know why! There's no reason why it's happening; I just don't know. I was reading about osteosarcoma and how it's common in teens and stuff(although I already went through my "growth spurt"). I don't know If the symptoms might be the same, but if any of you know anything, please help. And I know you're going to tell me to go to the doctor....I am going, but I wanted to ask anyways. I've had stuff with y knee before and I had physical therapy. It was called patellafemoral syndrome. It's still there but I stopped therapy. My bones in general(arms and stuff)are generally ache, don't know why either. What do you think this is? Cancer? :[ Thanks
Thanks but, I don't think it's because I stopped therapy because that was for my knee and I stopped therapy almost 3 years ago.