I'm 19 With Knees Worse Than My Mom?

5 Years ago I had a "typical teenage virus" attack my knees causing them to swell and be really sore. It felt like if U were blowing up a balloon to its extent, letting air out, and blowing it up again. In my knees. They have been bad since then but the last year they've gotten a lot worse and really sore. My legs go numb if I sit on the floor (like they fall asleep) and from 4 hours total of walking around town today while shopping and photography, my knees are throbbing and in a lot of pain, almost like growing pains if you understand. I'm wondering if you know any exercises I can do, supplements I can take, vitamins, over the counter medicine.. Anything.. I had x-rays done on them a few weeks ago but have not heard back yet. I need some help please!!! I also have a really bad lower back and they usually coincide.