Question: Can I rule out osteosarcoma (or any other bone cancer) as the cause to the pain in my legs?

I've had on-and-off pain in my legs for years and I am a fifteen-year-old female. The pain is in my knees, hips, both femurs, and both calves. (Feels like tibia?) I also get pain in my upper arms, however this pain is rare and always very sharp. While the much more common pain in my legs, varies in severity.

When it initially began the pain was occasional and pretty mild. Now it's to the point where I frequently limp whenever the pain comes back. (Although it is still sometimes mild) And no more than maybe two or three bones/joints hurt at a time. I seldom have pain in both legs simultaneously, but whenever I do it's never the same bone/joint.

The pain comes and goes as it pleases, anytime of the day, no matter what I'm doing. And it lasts anywhere from 5-35 minutes for the most part. I'd like to see a doctor about it pretty soon, but my mother is waiting until my sixteen-year-old checkup, which is in four months. (Despite the fact that I turn sixteen in one month)

She keeps teasing me by saying that I have bone cancer or a brain tumor. (Brain tumor joke is far fetched and due to other problems) And quite frankly I'd like to know whether or not I can rule it out before my checkup in four months.

Thanks to anyone who takes the time to read and respond! :)

Okay, thank you. So this isn't anything too serious?