First off, I would not give medication unless you know what the issue is, over medication can cause things to become worse.
It'll be important to keep your fish's environment in top condition while he is sick to decrease any environmental factors that can make it worse. Make sure you have clean water and temperature in the high 70s F. You should make sure ammonia levels are low.
Breathing heavy, can mean many things, is your water clean at the moment heavy breathing can be a sign of low oxygen in the water. Also it could mean he is having trouble aquiring oxygen through his gills, you should lower the water level for him if he is not swimming so he can access the top pf the water for oxygen through his labyrinth organ. If you don't feel comfortable lowering the water you may want to invest in an air stone to provide extra oxygen to your fishie.
Now can you describe the white looking thing on his back???, the photos make it blurr. It looks like it could be a fungus of some sort, but not 100% sure. Since you have gotten your fish 2 years ago, he may be old and more prone to infections.