well, there you go.. A quick google would suggest that low iron can in fact cause lengthy heavy AF bleeding. I would pop along to your GP during the week & ask them to do a full blood body count. Also start on some iron supplements.

Also this may be of interest re the clots
Check your hormones – too high estrogen or too low progesterone can cause heavy periods. I often see this in peri-menopausal women or women who do not ovulate regularly because their progesterone is very low. Elevated estrogen levels can also increase the amount of clots.