I cannot remember the last time I slept four or five nights in a row. I don't think I ever did so for over a decade. Maybe about four or five nights in a year perhaps. The rest of the time, I sleep a little during the day (sometimes normal seven hours if lucky).. or often, I don't sleep at all. When I'm working, I don't sleep at all usually.
I've no money for proper light therapy, but some measure of that helps in my experience. E.g. no computers after a certain time.. exposure to natural sunlight (lots of it) during the day... dim your lights after a certain time...
I often take showers and do other things like walking around the house in complete darkness these days. That's too extreme and can cause injuries if you're not used to it, but just dimming the lights a little should help. If you can do it, try getting some of Bob Ross (or some similarly relaxing tapes) videos, play the sound of natural rain and lie back. You may probably still not sleep, but it can help keep you away from thinking negative thoughts in circles.. especially thinking about why you're not asleep yet. I've been in your spot before, working stressful jobs (cop, teacher, others)... so I know where you're coming from. Instead of thinking "I can't sleep" try "I can get some rest, even if it's not always sleep"... May reduce the performance anxiety, or at least that was my experience.
@TheAristocrat: Coincidence? I've the exact same experience.