You're over a full week like this with no improvement? Your boy is obviously stressed but I can't imagine it's not time for some meds.. At least look into it since you may need to order.
For bacterial infections you're looking for Kanaplex and Focus by Seachem or Maracyn and Maracyn 2 in combo. Skinny might suggest internal parasites but since he's not eaten in over a week that could account for that as well. Metrodazinole and Focus by seachem or a premade antiparasite pellet would treat this, if it came to it, but I'd venture it's bacterial at this point.
What did his poops look like?
Start with the epsoms but if you see no improvement over the next couple/few days meds are needed. Honestly, I think they're needed now but I understand wanting to try epsoms first.. it's just.. he's not bloated..so IDK.