The condition of getting urge to eat non-nutritive substance(like slate pencils) is called Pica.
It is usually associated with deficiency of minerals in the body..mostly Iron Deficiency Anemia
Effects on health due to consumption of such non-nutritive substance may be in the form of infections, intestinal obstruction
, etc. in addition to the effects caused by the deficient mineral/nutrient.
So...it will be better to get your blood test
done to determine your hemoglobin
Management will be directed towards correcting the deficient nutrient in the body.
Best thing is to eat a healthy diet, avoid stress, get good sleep, think positive and stay happy.
Wishing you a Healthy Life.