Big problem help

Can you take a pic and uploaded?

It sounds more like some sort of a fungal or bacterial infection if you have scales missing ans a coat of something overing the body and eyes.

A pic would really help.

 

BTW, I wouldn't dose the tank with a medication especially if you're not sure what it is. If anything, baths/dips are a safer way to go for the system as a whole.

 

I agree with not treating the entire tank before properly diagnosed. The safer way to go is prob a salt water dip or general treatment meds such as 'stress coat'. I doubt that it would be ick. The white spots would have clearly been noticed on the fins, granted everything in your tank isn't completely white. If it is ick however, it has progressed to a stage which shouldn't have been unnoticed for a while now.
1. Is he scratching himself on rocks/ornaments in the tank?
2. Is he eating anything?
3. If you can, what color are his feces?
4. Do the other fish in the tank show signs of illness?(Not eating, Scratching themselves on ornaments)
5. swimming lethargically?
6. Have any other fish been introduced to the tank lately?