During school i get sidetracked when im faced with a difficult question. but when i drink coffee i dont get sidetracked. so my question is, is it possible for my body to lack a certain chemical that causes me to lose focus?

Attention deficit : Difficulty with losing focus in a teenager is often caused by tension definite disorder. Diet can make this better or worse caffeine can help with this improving the focus. Multiple medications prescription are effective along with counseling and therapy to help attention deficit disorder. Recommend you see a pediatrician or a psychologist who specializes in this for diagnosis and treatment

Not unusual: Humans have relied on stimulants like caffeine for centuries to improve focus. Whether this is from the caffeine in coffee or chewing coca leaves in the Andes this is nothing new. Proper sleep,nutrition,good health & exercise give you the best baseline for functioning well. If you think there is something wrong get a checkup & discuss this with your doc.