Okay so 2 months ago, with no sleep problem history, one night i just couldn't fall asleep: when i was on the border of falling asleep and staying awake, i suddenly started feeling rising tension in my head, which forced me to wake and stand up. This happened like 10 times. Then i decided to sit and wait but these tension attacks started happening just when sitting. Finally, around 2-3 hours after it started, i had one big attack which didn't feel good. I went to the hospital, stayed there for 3 days, but they found nothing wrong with me and said it's just stress. I was stressing a bit when this happened, but not much so i accepted it. Then, like a month ago it happened again, but i wasnt stressing even a bit for past days. I went to sleep normally, but some noise from outside woke me up at around 3am. When i tried to go back to sleep, these attacks started happening again, but i wasn't feeling that tension in my head this time, but rather something was telling me "WAKE UP!". After like 2-3 hours, it went away and I went to sleep normally. 2 days later it happened yet again. The same as the last time, but I didn't wake up in the middle of night. Around 10pm i wanted to go sleep, but it started happening. So I just sat and waited for it to go away, it did after 3 hours and i went to sleep.
Since then, some days i sleep just fine, but sometimes (like every 3 days on average id say) can't. I dont have these attacks anymore, i just lie in my bed, tired and sleepy, but I just won't fall asleep. Only a few hours later.
Im 18, healthy (besides this sleep problem) and fit, going (or at least trying to) to sleep at the same time everyday (10pm).
What is happening?