Pica, Iron, and Comet
Please go to a doctor immediately. It sounds like you need to also see a therapist, who could help you with cognitive therapy to recognize when you crave Comet the most. You say you have a hard time remembering to take your iron, what if when you crave the Comet, you take an iron pill before you go for the Comet? Even if you still wind up eating Comet, you will have taken your iron.
I was addicted to Altoids Smalls for 2 years, 2-3 packs a day. I eventually found out I was getting close to anemic, and started taking iron. Within two or three weeks I lost all of my Altoid cravings. I didn't realize they were related until just recently, and that I had pica.
A doctor can help you with the best kind of iron to take, and in the right way. A therapist can help you address why you go for Comet when you are stressed or sad.
Maybe you went already. I really hope so!