My knees crack repeatedly...?

This has been happening since I was little. I'll unbend my knee and it'll pop. Then I'll bend it and unbend it again and it'll pop again. I'll do that a few times, sometimes it even goes to 20 times, and then it'll give a loud crack and it won't pop anymore. Also, my ankles crack when i turn them around in a circle, my toes crack, my knuckles, my neck only cracks if its stiff, my back gives a high pitched crack when i straighten up but a low pitched crack when i twist it. my wrists also crack when i turn them around in a circle, and my hips crack when I stand up. im only 14. Why do my knees pop so much and then give a loud crack? and why do the rest of my bones crack?