Remicade effectiveness

I have both rather severe Lupus and RA and was started on Remicade 4 months ago. After my first dose I felt like I had been given a new life. My days where virtually pain free. Then a week later, I got put on Levoquin (antibiotic) for a still uncertain stomach infection. I had a horrible reaction to that drug ( Major muscle pain and then an allergic reaction when I started the second round of it). Anyway, since then, I've never recieved the same relief from the Remicade; it helps some but nothing near how I felt after the first dose. I've had 3 doses since and they even increased my dose the last time. I'm not sure what to think. Is this common? And how quickly after the infusion should I feel better (its been a week already and I still don't feel like its helped).