Betta Fish: Whats wrong with my betta?

My male betta fish was looking off lately, he is in a quarantine tank right now. Im waiting to see if he poops since he looks bloated it’s been 2 days and he has not. I went to petco and (i dont trust them) and the guy said he might have a parasite, which i was inclined to believe until i asked if he had epsom salt and he handed me aquarium salt 💀. That aside, Ive tried fasting so far, epsom salts on the way in the mail, i have medicine available if it is a parasite. Im not to sure if it IS one i dont want to medicate him if i dont have to. His symptoms are: Slightly floating to the top almost like swim bladder but less severe, he use to be stationary and sit in one spot but hes getting his sas and his energy back by day, he looks bloated. He has looked bloated for a little bit, at first i thought he was just big, i could be over feeding him? I have 3 other betta fish who are being fed the same thing and are an ideal weight, so im inclined to believe it may be a parasite or tumor. there is a white dot by his butt that could be a work blocking his way to poop. i apologize if the pictures are low quality.