Good morning! I’m sorry to hear that you have been having trouble with sleeping 
. I have insomnia, so I have a prescribed medication to help me sleep… however, depending on what is going on with me decides how well it will work.
If it continues after trying some of these options, I would consult either a psychiatrist or your primary care doctor if they are available.
I drink either - Chamomile Tea 
or Chamomile & Lavender 
tea sometimes when I am getting ready for bed.
Play sleep stories or sounds. The Calm app, Insight Timer app, & I believe Spotify all have stories, sounds, podcasts, or playlists of some kind. I listen to Celtic Relaxation/Meditation 
music on low from Spotify. Sometimes if silence is too much I will play it on low through my Google Home in the living room or use headphones if I am going somewhere that I will be waiting in line or in a waiting room or shopping.
Journal whatever is on your mind before bed.
Turning off electronics & watching something that isn’t really too brain engaging, mindless TV or a meditation
Exam Stress and Poor Sleep this may have some ideas in the replies for you.
The Magic of Sleep and Dreaming 
Relaxing the mind for deep sleep
I hope some of those help & as @Elle mentioned Melatonin can work. My daughter had to take it when she was younger. I believe what we used was ZZZs (Vicks) Melatonin gummies. They would have sales two for one all the time. They worked for her & she liked to keep them in the refrigerator, when she got older she would take two of them then we just switched her to the regular so she was back to taking one each night. Hers were all-natural/organic & recommended by her primary care doctor. (I didn’t want her on a prescription type of medication at such a young age)
I live in a state where marijuana is also legal & sometimes I just need a gummy to relax enough to be able to settle down & get ready for sleep. I will also say that I have a medical card & it was recommended by two of my providers. One was mental health & the other was my primary care doctor & I guess we can include the doctor that issued the card for me to register with the state to go to the dispensary. 
(Please do not try this if it is not legal where you are & it’s not something that you entertain as an option or have decided not to use)