It sounds like you have let the water get out of whack so as Spishkey said, start doing large and frequent water changes to get things back to normal. If you have been using antibiotics, you may have damaged your biological filter and are now finding yourself in the middle of a fish-in cycle. Monitor your water and do the needed water changes and things should get much better quickly. I become concerned when I see people using a lot of medications because I know it can upset the balance in your tank so easily.