I can't find a concrete answer anywhere; is marijuana addictive or not? and what if the smoker has an addictive/obsessive personality?

You haven't looked: Marijuana dependency (addiction) is a diagnostic term used by both the DSM in the US, and the World Health Organization guidelines elsewhere. You are on medications that indicate either a bipolar diagnosis or some form of thought disorder (schizophrenia, schizoaffective disorder etc.). Marijuana is particularly bad for you, and at your age affects your ability to learn, remember and intelligence.