Constructive Underage Possession in Pennsylvania

i was arrested a few days ago for simple possession and a constructive underage i did have marijuana on me when i was arrested and there was beer in the car however i was not drinking ( constructive underage) i was brought to the station my parents called once they arrived i was breathalyzed and had not been drinking and told if i gave a truthful statement and cooperated it would make things easier so i told them everything in the statement then a officer told me since it was my first offense and i had high grades and expectations of myself that the case would be herd in by a magistrate and the constructive underage possibly dropped and if not both charges could be expunged soon after. however my father called and they said both charges would follow me for a long time even though I am only 17 and i would not be able to become a teacher because of the charges (i have always wanted to become a teacher and graduate from Penn State University)
i cannot afford a lawyer but will these charges follow me to college?
and if i get them expunged will they still count against me ?
or will they possibly get dismissed after the hearing or when i turn 18?

the local police have told us many different things and i have no clue
what to believe

You have to weigh the cost of a lawyer against the impact on your future. Within that context you can afford a lawyer, and it sounds like you need to afford a lawyer. I doubt a MIP alcohol will affect your future much, but a drug offense is more significant, particularly if your father is correct and it would preclude your eligibility for teaching jobs in your state.