It sounds like the dentist that treated you may not have given you an informed consent, and very likely for the treatment to be failing, his skill with placing the new restorations seems to be lacking.
I mention the informed consent because the composites contain elements that can also be harmful to people, and removing one for another may not have been a decision you may have wanted to make given all the information.
Secondly, composite fillings are very sensitive to the moisture when being placed and are not as forgiving as Amalgam is. So there could be a whole host of questions to your dentist about the care he gave.