Chickflick, I think the number one thing to suspect with low Iron when no obvious cause can be found is an overgrowth of candida. You can't depend on doctors finding this and they are not going to look for it because they don't believe it exists. They would have to do a stool test and an antibody test can confirm it but there are only a couple of labs in the country that does this. Here's a test you can take to give you some idea if this might be the problem. If this is the problem and you have caught it in the early stages you might correct it with just a good probiotic with multiple strains of bacteria, also yellow dock root is one of the best Iron supplements.