Hey there kibbles,
like duck said its not that ur immuined to the medication its that most likely its progressing.
Take me for example i was on mtx, prednisone, and naproxen for 8 yrs and i was great. there was times when i completly for got that i had RA. Then recently those meds just werent cutting it any more. My doc talked about going on enbrel or remicade, needless to say i was scared to death. after trying diffrent kind of oral meds that would only work for about 1 month (sulfasalazine+plaquanile). I finally gave in after 1 year and went on remicade i just had my 3rd infusion and man do i feel better a lot better i only wish that i had the courage earlier to go on the remicade a year ago, but no regrets at least now i know that the remicade truly was one of the last resorts for my condition and i wont be wondering what IF. Well kibbles that my story hope that it helped you in some way. and GOOD LUCK