I had similar symptoms that started around the same age as you, but mine progressed slower. I had bad shoulder pain at age 18 and then slowly the knees started to bother me and then the feet from time to time. Mine happened so slow that I went un-diagnosed for a looong time.
Looking back over the 14 years or so and what I was dealing with it is very obvious what was happening, in retrospect. With the pain - especially the knee pain - I would avoid doing certain things including things like going to the beach with friends just because I couldn't be cramped up in a car with friends for three hours. Heck, just a few weeks ago when my knee was pretty full of fluid I turned down free symphony tickets and also some free NHL tickets a few weeks before that (I went to the symphony once on a "bad knee day" and all I can remember of the show was me shifting around in pain!). The fatigue you mentioned was actually just as crippling as the pain, and interfered with my life quite a lot. I won't go into it, but if anyone ever sees you looking sleepy and then calls you "lazy", punch that person in the face immediately.
I envy you quite a bit because at an early age you seem to have a buzz of activity going on all around your syptoms with doctors and medications and such. If the baby meds aren't working I think it is a good idea to move up to a DMAR drug to help stave off damage to joints.
Arthritis (poss. RA) - Doc scripts: Enbrel, Methotrexate, Celebrex, Folic acid. Self-scripts: Glucosamine, GNC Men's Sport multi-vitamin.