“Random pain in lower joints?”

I get random pain in my joints, mostly my knees or hips, and sometimes my ankles. The pain can last from 30 seconds to 5 minutes and vary in pain. I have a high tolerance to pain and can feel like I simply ran into something (noticeable but doesn't bother me), to me needing to lean on a certain side of my body or just stop walking (or sit down) entirely. I am only eight pounds overweight and am using a safe diet to lose weight. I often wear my flip-flops or sneakers which both have feet support. I did experience a few close calls in my younger teen years where I would almost dislocate my knee cap (twice on right and once on left). When I got x-rays, the doctor said there was nothing wrong and that it was a normal side effect of being flexible. I am not a gymnast or anything just a flexible person that can only do one kind of splits (the easy way), I can't even do a back-flip. I am almost 17 and would like to understand myself and my body better.