I have had weird sleeping issues all my life, and the key for me to falling asleep was when I found out that our body gets tired not when it is warm, but when it warms up. So next time you can't fall asleep, take off the blankets, make sure your room is cold, and then get really, uncomfortably cold, and stay that way for at least 15 minutes. Then, and this is key, cover your whole body only with your sheet, and then…
I remember reading in A study that feet warming up was the factor best correlates to falling asleep (I remember it from only a few years ago, maybe it was a follow-up to this 1999 study? [1])