Insomnia problem. From 2 years almost.

Hello Doctor, I am not able to sleep properly whole night. Headache also started after 4-5 days due to not getting enough sleep. The same issue occurs once after 3-4 months from last two year and it continues to 15-20 days. I usually go to bed before 11 and I can fall asleep in 5-10 minutes and I sleep well,  but I don't know why this type of insomnia repeated again and again. I have no stress, depression, anxiety, nor I use electronic devices at night. I have also taken meals property and light food at night. My height is 150cm and weight is 47kg. I work in IT. Age-25 I don't know whether above information is relevant or not. Please let me know what's wrong in my daily routine, due to which I have to suffer after every 3-4 months. I also got small hematoma in my brain in November 2016. But insomnia issue is from 2 years almost. Thanks in advance. :-)