Are you consuming caffeine during the day? If so, either move any caffeine consumption to the morning or preferably cut it out completely. Also, do not nap during the day.
Now, there are a bunch of things that can cause insomnia besides that. Depression can cause insomnia, and insomnia can cause depression. It’s important to get the sleep issue under control.
How’s the noise and light situation? Even a small computer light can keep a person up. If light’s a problem, one can get one of those masks.
Are you getting physically tired during the day? Usually when one is physically tired, he sleeps better, but it’s not recommended doing exercise just before bed.
Websites recommend having a routine, going to bed at the same time every night and not doing TV watching and all in bed, to associate bed with sleep.
Before bed, it’s suggested to have a winding down, quiet time.
Stress and worries can make it harder to sleep, of course.
Natural sleep aids are camomile tea and Valerian root which comes in capsule form.
Certain physiological conditions can also cause insomnia from sleep apnea (where one has trouble breathing time and again, causing a person to wake up many times, not get a restful sleep), to overactive thyroid, etc. For a partial list of physical conditions, see below:
mayoclinic.org/diseases-conditions/insomnia/basics/causes/con-20024293
I lived in a city that had a hospital with a sleep clinic for tough cases of sleep disorders.
If you want to try medication, there are over-the-counter sleep aids. For tougher cases, there are prescription sleep aids.
If it persists, might want to mention this to your doctor.