sick betta? please help :(

Okay so for starters i’ve had my boy Fidel for two months, he’s always been very timid and hides a lot but i’ve noticed him hiding and even resting at the bottom of the tank for long periods of time. at first i thought, oh maybe my water is dirty or the parameters are off? nope. my pH was 6.8 (currently 7.2) my alkalinity was a little low but i’ve raised it and it’s now at 80 ppm my nitrite and anomia levels are 0, and on top of that i’ve just deep cleaned the entire tank and i’ve treated the water with acrivelt to help with his wounds on his body :(. i’m 100% he has parasites because of the lethargy, the cloudy eyes, eating normally but still losing weight, the wounds on his body, him not flaring anymore, etc. I really need help on what to do, i’m relatively new to fish keeping so i’m not too informed on types of parasites or even other illnesses, all i know from what i’ve been investigating is that it looks like a case of internal parasites ? i don’t know if he already had them when i got him because my tank is relatively new and and i have snails from another tank with a perfectly healthy betta, so i have discarded the idea of the parasites coming from the snails 😭. can anyone recommend medicine? should it be water treatment or food medicine? how can i prevent this in the future?