I started treating him for septicemia, I think he probably have it because his pectoral fin is kind of bloody.
He is doing a little better today, no spazzes so far but he is still breathing incredibly fast and hard. I emailed a experienced fish keeper from my aquarium society and he said, bubbles coming out of gills regularly might indicate the fish's gills aren't functioning properly. So I am just keeping him close to the top of the tank with lots of silk plants to rest on, that way he can directly take in air.
fingerscrossed he can recover by next week and move to the 10 gallon!