photos?
How often are you changing your water and vacuuming the substrate? If you haven't done so yet, I would do 75% water change, vacuum, and clean out your filter (dump water, wipe down the surfaces, squeeze media in a bucket of tank water). You need to keep your water clean so that your fish can recover. I would also add salt at 1 tbs./10 gallons.
If your fish gets worse, please send an update so that we can help you.