Since I don't have your bloodwork nor do I know what you were sick with I obviously can not diagnose you, but sports anemia should be considered.
Many endurance athletes get an increase in their plasma volume (blood volume) as an effect of training. The RBC's actually increase as well but since the non-RBC portion increases to a greater degree, there is a dilution of the amount of RBC's per volume, thus giving the impression of an anemia.
Also, runners can have an increased breakdown of RBC's due to the impact of running on the heel/foot. They call it heel-strike hemolysis.
You can Google sports anemia for more information.
As always, if you are concerned, ask your doctor.