The above posts are all correct. Different causes for different people, and it seems to me, different causes for the individual at different times.

Insomnia sucks and it can really mess up your life. I know from personal experience, including tonight. It is 3:00 am now. Got up an hour ago and could not get back to sleep. Lost my job a month ago. I can't really blame anyone there. My ability to do even the simplest tasks was gone. I wasn't safe and worked around/with 480volt doing maintenance in industrial setting, so .......

You did not specify whether you had problems getting to sleep or staying asleep or even both. For getting to sleep over the counter aids may help. In my case the antihistamines cause my restless legs to flare to the point that the prescription meds I take don't work. But good ol' benadryl might work for you.

Prescription meds are hard to get! If you have severe long term problems you might be able to. For sleep onset ramelteon really worked for me, but wears off quickly. Works for an hour or so.

If you can list some of your particulars I might have some possible help. I have gone weeks, literally, with no sleep or bits and pieces of "micro sleep."

Please remember , you are not alone.