My tiger oscar has been acting fishy?

Is it scratching itself on the gravel and decorations as if it is itching? if so, it could have parasites. check for any signs of ich (tiny white spots) as for his eating, try feeding a few pieces of food at a time, not a full feeding. Does he get his mouth full then spit it out? if so, what are you feeding him? some pellets might be too hard at first for him. Try pre-soaking a few pellets before feeding. It's what I do for my bettas.