Moonbeam / Betta Bloated Stomach

Hi
I'm still struggling with moonbeam .  He was looking a bit slimmer then I thought he looked big again . So I fasted him for a day yesterday . Fed a little daphnia this morning . And gave him an Epsom salt bath for ten mins .
He can swim but is definitely lounging on his weed much more . I've reduced his food and am just giving daphnia .
This has been going on for over a month now . I'm going to the fish shops at the weekend and was wondering if there is anything else I could try medicine wise . I did treat him with myxazin when this started . I also have esha at home.
What can be wrong with him ? Could he have something going on internally that's eventually going to kill him. ?
I've looked at him with a magnifying glass and his body fins look perfect .
I never see him poo . When I feed him he jumps on it like he's starving .
What else can I do ?
Ally