Hi, M.. I have to agree with the idea that you need to be tested for anemia yourself. If your baby isn't getting enough iron, something odd is going on here. Definitely get him going with a multivitamin supplement that contains iron. Your pediatrician should have prescribed this for you. Call them back and let them know you want this. The doctor should be able to just call it into your pharmacy.
Meanwhile, as I said, you need to get your own blood tested for anemia. Most likely your iron stores were drained during pregnancy and breastfeeding.
If vitamins for you and your son doesn't clear up the anemia, I would get both of you tested for lead. I doubt this is the issue, but occasionally homes have materials in them that contain lead. And lead absorption into the body can block iron absorption from food and vitamins.
Also, with his anemia problem, it might be good to get your son drinking a little fruit juice, once or twice per day. Generally white grape juice, then apple juice. The vitamin C will help his body absorb the iron better.
You can dilute the fruit juice: half water/half juice. To make it easier to digest.