I believe your fish is sick. Unfortunately, after reading the replies you have received they are not providing you with the correct advice.
It's very well known fact that Oscars have an issue with hole in the head disease with is cause by an internal parasite called s. Vortens. The great of news is there is a cure, but before we talk about medicating I would like it if you can tell me a bit more about your fish.
First, can you provide more photos of he his area looking from the front of him. This way you can focus on his sensory pits and that's a sure fire way to diagnose. The clear poop and the lack of appetite is also a red light for HITH.
Besides pictures please provide as much info about water parameters, diet, tank mates, possible stressors, tank temp, how long you have had the fish, size of aquarium, ect.
In the mean time don't start randomly treating untill we can confirm what we are dealing with. I have first hand experience with this parasite and can provide you with help moving forward. Keep in mind this is not an easy quick fix but rather a fight which can be difficult to win.
Read this great article for starters and also do alot of googling about s. Vortens and hole in the head disease and Oscars and cichlids.
Spironucleus - Hole In The Head, Head and Lateral Line Disease