If your problem seems to be at 6kHz then please, get your hearing tested before you do anything else. You can test up to 8kHz "everywhere".
And second thing - you can't really trust your headphones or speakers. Especially when you go above 8kHz. For an example my cheap headset at my work place has a huge dip at 7kHz. First I thought that I have moderate hearing loss at 7kHz but then I tried my mid priced headphones at home and i heard 7kHz tones well. To avoid this kind of confusion, audiograms at hospitals are calibrated accurately every month (atleast here in Finland).
So get your hearing tested rather than losing your nights sleep...
And yes, if you have 90dB hearing loss at some frequency and you keep playing 110dB sounds to hear certain frequencies - that can damage your hearing even more.