Not sure if this is a possibility for you but if you are mediterranean origin then maybe it is not your iron levels but your blood make-up.
Hubby was born in North Africa. He kept getting send to one hematologist after another because of his low red cell count.
Then he found a specialist who took one look at him and laughed. He informed him that 'his' normal was not everyone else's normal and that North Afraicans have a specific blood type that does not hold iron the same way...it was the first that I had heard of it but since then we have stopped panicking!
If not, I agree with Scott...Look higher up. Check for occult blood in the stool. Losing iron that quickly is not normal. Unless your body is losing blood your levels should not be dropping so quickly. Or your body/blood does not 'affix' iron to it...
Just a thought.