Then you are not alone. About a third of adults all round the globe at some time or the other experience some type of sleep disorder during their lifetime. For your information, the female sex and the advanced age category have an increased prevalence of sleep disorders.
Insomnia is difficulty in initiating or maintaining sleep.
If you do, then you are wrong for insomnia is not an illness but instead is just a symptom that can have many different causes. Insomnia may be transient or persistent. Transient insomnia is most often associated with anxiety, either as a sequela to an anxious experience or in anticipation of an anxiety provoking experience eg a job interview or prior to an exam. Sometimes it can be associated with grief, loss, or any life change. Specific treatment for the condition is usually not required.