Prescribed compozine for pollen allergy being a psychotic drug could that have change my brain chemistry was 17 at the time / did have severe allerg?

Not exactly sure: What you are asking, but Compazine (prochlorperazine) should not cause allergies to pollen. If i haven't answered your question then please clarify further and re-ask.

Unlikely: long-term alteration of brain chemistry after using prochlorperazine for definitive amount of time in the distant past has not been shown in studies that monitor safety.