Quick question, just wondering. I'm the vocalist of a screamo band in which I could scream almost constantly for an hour, and it isn't literally screaming like you would if you saw some invading army, but more like a kind-of scream or a distortion of the voice. I can go on for a very long time and my voice never dies out, it's not like I wind up coughing blood up or any thing, but ever since I've started I have lost a lot of my high notes in singing, and some times it kind of hurts to cough during practice. I've tried to practice with proper technique, but am I doing any permanent damage to my voice?

Any answers/technique suggestions? I'm needing some help, but please, no "U IS NOT SUPPOSED TEH BE DOIN DAT SO YEH STOP NOW" because that isn't of much benefit to me and I know some artists that have been doing it for almost a decade and they are doing okay.