Nah, I've definitely subjected mine to a fair bit of abuse before wisening up, so yeah, I have only myself to blame! It really hasn't negatively affected me at all though, only in absolute silence does what little ringing there is get a bit vexing
But that is absolutely normal, even my doctor told me everyone hears a slight hiss when in total silence, there's no way around to it, I think it's the blood in the brain flowing or something
i got some custom made plugs from http://www.sensaphonics.com/ and they work great! i have a set of 25db and 9db filters. they also do hearing tests and ear cleanings, actually i gotta go back soon to get tested again.
Mine craps out around 15k. But, I'm 33 and haven't really taken good care of my hearing at all. To be honest, it hasn't changed from the time that I was about 22 years old.