A little more information would be very useful. How big is the tank, what fish are in it, what is the temperature, and what are the water stats (Ammonia, nitrite, ntirate, and pH)?
Why can't you treat it anymore? I've just finished with a bout of Ich. It was awful, lost most of my fish but some survived so I'm glad that I didn't give up.
Ick can take longer than a week to cure, sometimes at least two courses, turn temp up to 30, increase aeration as med and high temp will reduce 02 in the water.
Check the instructions as you have corys and can be sensitive to the meds, plus with bottom dwellers the aeration must be raised as the 02 will be low there if not.