Iron deficiency. Iron deficiency causes anemia, fatigue, weak or malformed nails, and pica. Pica is when you crave strange non-food items. Typically, affected individuals munch ice but I've had patients eat wallboard, chalk, dirt, starch, and mattress stuffing. You need to see a doctor and get a cbc, iron, tibc, and ferritin. You may also need tests to rule out serious conditions such as ulcers and cancer.