I used to have trouble falling asleep until I started doing tris.
Now the problem seems to be staying asleep. erg.
There is no computer or tv in the bedroom. I don't use the bedroom for anything but sleep. If I do get up, I don't turn the light on. I think I shall have to start doing a sleep log. That might give me some more clues.
I don't do caffeine EVER any later than 3-4pm, since I know that affects me - I rarely do it anyway (not a coffee drinker), unless I've had an especially bad sleep night. I also know alcohol affects me, so I avoid that in the evenings during the week... and unless I know I can sleep in the next day.
I have even refrained from drinking liquids within an hour or two of bedtime.
I could see it being stress, or too much on my mind... when I do wake up I try to relax and repeat to myself "Relax" or if I wake up and worry, I tell myself "Relax and go to sleep, there is nothing you can do about that right now".
It's just frustrating because of the effect it can have on my workouts, and thus my training/racing goals.
I'm going to give the sleep log a shot.
It sounds like it's stress related- you have a lot on your mind, and it's waking you up at night. Try leaving a notepad by your bed, and writing down all of those little things nagging you right before bed. If you do wake up, and find your mind racing, write those things down.
For me, my brain is always listing off the things I need to do, and I am always afraid I will forget them. So, if I have a notepad by my bed, I can write stuff down and not have to keep it racing through my brain.
If I can't fall asleep, I focus on deep breathing, and counting backwards from 500. I try to go really slow, and focus on the number, so I don't just race backwards. This way, I am forcefully clearing my mind, and eventually (usually around 410) I will fall asleep.