The problem is that you have a Comet Goldfish that can reach a foot long or more in a death trap fish bowl.
This fish has no filtration and it's gills are literally rotting from his own decomposing feces. It's suffocating from Ammonia that damages gill tissue.
What you need to do right now as soon as you finish reading this is get some water, add dechlorinator (if you don't have that use bottled drinking water) and change out the water in the fish bowl.
Now, tomorrow you will need to either take the fish back or upgrade to at least a 20 gallon tank, but you must know that this sized tank will only sustain the fish for a while. Remember I said this fish can grow a foot long or more so they really need to be in at least a 75 gallon tank for adult size. Ponds are best.
When you get the new tank, also get a filter for 40 gallon tanks. You will also need liquid testing kits for Ammonia, Nitrite and Nitrate as the tank will need to cycle for a few months. A gravel vac is a good thing to have as well when doing frequent water changes (for you, every day until the cycle is complete).
Please, do not EVER purchase a fish or any type of pet without researching it as much as possible before hand. Bowls are not meant for fish and it's a very common mistake a lot of new fish owners make. Just do the right thing to save this fish's life. Please, check out the links.
