Consider yourself fortunate to still have some degree of hearing left to work with. Keep in mind that as we age, men tend to lose the high frequency sounds, while women tend to lose the low frequency sounds. The best way to compensate for this is with hearing aids - in fact, it is the only way. Hearing aids will allow you to adjust and amplify the frequency that you have lost, thereby correcting your EQ so you will hear the sounds normally. Monitors will not do this. I, and several others on this site, have experienced the same problem over the years, and I found myself cranking up the high EQ on the keyboard, higher and higher so I could hear those high hat cymbals, strings, steel guitars, etc, while audience members with normal hearing were complaining that the sound was too loud. After purchasing hearing aids, I knew exactly what they were talking about, and I was able to make the adjustments.

Hope this helps,

Gary