insomnia troubles, help please

for the last three weeks, i've been having problems sleeping. it's winter break, so i would assume that my body would want a break from college (i'm 20 btw) and just sleep better. but, every night it takes me hours to fall asleep, and even if i do fall asleep i'll wake up 3 hours later for no reason. most nights lately i've been staying up until 7am for no reason, and not even able to nap in the afternoon for balance. i used to be a good, deep sleeper during the semester. i would get 7-8 hours of uninterrupted sleep, and even sometimes nap in the afternoon. but now i just cannot. i haven't changed my diet or any exercise stuff (i usually just go for walks because they are easy lol), i try to stay off my phone for as long as possible before i try to sleep, but i'm just getting so frustrated at not being able to sleep. i've tried a few otc sleep aids but they don't help me sleep through the night, and they give me horrible nightmares. what other more natural remedies or vitamins could you recommend? i would really appreciate the help!