Oscar just lying on its side for a week now

Question
About 2 weeks ago my tiger oscar who is about 10 years old jut started spending much of its time on the bottom, then began lying on its side, occasionally moving positions every 10-12 hours.  Went to our local fish store, and had the water tested, which was high in ammonia, pH, etc..we did a water change of about 40% and used bottle water (for the first time).  But the oscar is still on its side, not eating, breathing seems less every day.  Anything I can to revive the fish?  Or is his time?  
Please help Brittany.
Thanks,
Ernest

Answer
Continue doing frequent water changes, around 40% every other day until he recovers. Just keep using tap water with dechlorinator - you don't want to change too many things at once, it will just add to his stress. Use a remedy all (such as LifeGuard) and aquarium salt and just follow the directions on the packaging. Gravel Vacuuming would be a great idea as well.
You need to keep up on water changes, and be sure that you have a good filtration system. Oscars are meat eaters and therefore very messy and produce more waste than some other fish. You should also have at least a 55 gallon tank, because Oscars grow quite large.
Sorry this answer is so late in getting to you, I am using a friends computer because mie crashed due to a virus. Hope this helped.