Prepare to live your life in the depths of hell.
I kid, I kid. Kind of.
I deal with chronic insomnia and have done so for the better part of 2 decades.
I've sought professional help across the years, done sleep studies, been to specialists. Some of us just won't ever really sleep normally I've learned.
Psychological help, like talk to a therapist, could help if the issue is anxiety or depression that might have a proximal cause. Long-term anxiety or depression, and you really need to talk to a professional. That's the best bet if that is causing your insomnia.
The advice above is all great. I would add to develop a routine, do the same things every night before bed.
Couple other things: no smartphone use for a full hour before you go to sleep. 2 hours is better; the room temperature can be a trigger to wake or to sleep, be sure that it is a few degrees cooler at night. I live in socal, so that means aggressive air conditioner use; only use bed for sleeping and other purely bed-related stuff. Don't go to bed then watch TV or even read or anything. Only go to bed when you are ready to sleep; try a weighted blanket, the weight can signal your body to both relieve anxiety and to sleep.
I have problems both going to sleep and staying asleep or getting back to sleep when I wake up. The part you are dealing with can be the most frustrating. I'll try actually getting up for a bit when I can't get back to sleep. Don't lie there and fret about it, this can build frustration and make things worse. Sometimes I'll get up, go sit in a dimly lit room and read, from a real book, avoid the temptation to get out your smartphone or tablet or even computer or watch TV. These all are too stimulating and will guarantee I'm up. But most often I'll sit there and kind of like meditate. Listen to the sounds, be aware of my body, looking around the room without focusing on anything. Usually just 10 or 15 minutes and I'll be nodding back off again.
That's kind of the last one. Done kind of meditation before bed can work really well, both to get to sleep and stay or get back to sleep.
If nothing is working I'll use some melatonin, in extreme circumstances I have an array of prescription and non-prescription sleep aids, but I hate them all.
When it gets really bad I'll sometimes try true biphasic sleep for a while and plan to go to bed a little earlier and actually get up for an hour or two in the middle of the night, then do my normal bedtime routine again and sleep for another few hours.
Good luck, I hope you figure out what works for you.