You eat before bed, have a night light, sleep at different times in an inconsistent schedule, workout before bed, screen watch, sleep in too warm of an environment, have bright lights in ur room late at night, don’t get sunlight in the mornings and evenings, drink or smoke a lot? These are all things that’ll kill ur melatonin levels though also things I do as well though I’d recommend looking up breathing techniques and other stuff if you struggle to fall asleep along with vitamins that help