For the first time my knees, shins and even thighs have been paining a lot. They pain while walking and now even in general. What should I do? I'm 21

Let try to help. This injury is brought on by exerting too much pressure on the lower leg muscles or excessive impact on the muscle. F you some recondition and stretching exercise before doing any sport activates, use Motrin on a dial basis tell the condition improve , if did not check with your doctor. Good luck thank you.
Be carefull Please. To have this feeling on one side this means to me you have problem in the circulation of the neck please check out. Good luck.