Jay, it's hard to know exactly what is going on, but generally, ice damming is from a combination of poor ventilation and not enough insulation. Adding a frame on top the current roof, starting with vertical furring strips, is a good start - make sure air can freely get in the bottom, and exit at the top. The top exit is going to be tricky with proper endwall flashing.
A picture or two might also help people give you solutions.
