Is 3-6 hours of sleep enough?

I am generally not a good sleeper (insomnia). On a great night, I can fall asleep after an hour in bed. On a bad night, I will get in bed at 10:00, lay there for 8 hours, and then start my day. I average about 3-6 hours of sleep per night, even on weekends. I have tried all I can think of (white noise, maximum doses of melatonin, turning off all electronics, etc.). In the case that my situation cannot be remedied, could I make do with 3-6 hours of sleep for the remainder of high school and college? More specifically, would I risk any long-term or short-term consequences such as brain development or increases in acne? And does anyone else have suggestions on how to still do well while being sleep deprived (coffee, exercise etc)? Thanks for any advice.