Sorry about your experience. Your the opposite of most people. My Amalgams were definately screwing me up and I have no problems with composites.
When you had your Amalgams replaced, did you get them done with the proper protocol? Did you do Chelation therepy?
Amalgams should never be replaced unless the proper procedures are followed. And should always be followed up by chelation.
If either of these steps were not taken, I would say your problems are probably more related to mercury vapor from the removed Amalgams getting into you mouth and gums then from the plastic fillings. Mercury will piss off the immune system so much you will react to anything in the mouth. I would explore chelation before you blame it on the new fillings.