Sinus ct scan said retention cyst and mucosal edema in right maxillary. All other sinuses clear. Sinus infection? Do I need antibiotics? I head pressure, clear post nasal drip, I can breath through nose, sinus rinse easy, snot is clear/white blowin

Sinus. CT findings only. No indications for antibiotics given rest of your history.
Not. Believe I might have answered this question before. Your problem is more likely an allergic one than an infection. If the mucosal edema is >6 mm, the probability of a sinus infection is higher. Treat the allergy and the problem will likely improve.