First, I would say, calm down. It is a long term disease, as well as a long term treatment.
Be sure it is HITH/LLE. If you can provide some pictures, please do.
When my O's sensory pits really started to show, I got worried for a bit it was HITH, but, some Os pits just stand out better than others. Also, oscars can be quite clumbsy, and take out nasty gashes in their body that can heal up amazingly quick (about a week). Mine split his lip and it healed up mostly within a month and now you probably couldn't tell.
Number one thing to do is keeping the water as clean as you possibly can. Definitely under 20 ppm nitrates, but, as low as you can (under 10 ppm is much better if sanely possible with your water source). Of course no nitrite or ammonia. Make sure the filters are cleaned out regularly as well as the substrate ... if not well maintained, they can build up baddies that will affect your fish's health.
Number two thing ... varied diet with lots of vitamins. A well balanced diet is healthy for all life on this beautiful planet
Possible things that haven't been proven, but are followed by a lot ... remove carbon from your filters. Carbon is unnecessary with frequent water changes and a waste of money anyway ... use the space for more mechanical or biological filtration. It may be the fine dust leftover after rinsing it, or it going bad quicker than you replace it and leeching bad stuff back into the tank, but it is a worthy (and cost-saving) precaution in my opinion. The other thing is making sure there is not a short in the heater, I suppose with your hand, or a voltmeter when it/they kick on.
I am sure there are more things, but first and foremost is clean water and good nutrition.
I hope for the best for your fish and for your peace of mind.
