After sports I have tons of pain right below my knee knee but then it goes away until I play again?

One of two things. 1-stress fracure. 2- stress related injury.(chin splint). Check it out.
Possible stress fx. Bony pain that is activity-related needs to be assessed for the possibility of a stress injury (reaction or fracture depending upon severity). Xrays are included during the initial evaluation and exam. An MRI is often requested if pain persists despite adequate rest and even temporary immobilization in a brace or cast. Osgood-schlatter's disease is a particular stress injury to the tibial tubercle.