I have early onset arthritis too ~ mine set in at age 14. I have some days better than others, and FMQ is rough. But I do what others have suggested ~ move around, get up, stretch, when the lactic acid hits the muscles, it exacerbates the arthritis. Mine is degenerative arthritis, haven't been his with RA (yet) but know it could hit anytime. With the natural vitamin therapy, has your doc mentioned anything like turmeric or capsacins? Some days that helps mine (and I prefer the natural methods anyway) ~ I have an egg-yolk allergy, so cannot have the flue shot, cannot take beta-blockers, cannot manage with Imitrex or the others... so Lecithin (vit E) is my lifesaver, and the turmeric helps with pain too sometimes. I eat a lot of peppers in my diet, so I've got elevated capsacin levels anyway, for exactly this reason.
Don't give up! Do what you can each time, and go back to it and see if you can resume. Don't try and force it, you'll just cause yourself a lot of frustration :)