My ferritin level is a 0 and my hemoglobin is 7. my doctor is sending me to a hematologist. but what could these numbers indicate besides low iron?

Blood loss: Severe iron deficiency anemia usually stems from blood loss. Have you had external bleeding,black or red bloody stools, very heavy periods? The fact that you're not severely weakened suggests a gradual blood loss, rather than an acute hemorrhage. The hematologist is best qualified to evaluate and treat you and order the appropriate tests.