At your age there are various changes and challenges in life. Most of the fears are due to insecurities in life. More details of the symptoms and description is required to conclude whether it is due to axiety, depression, ocd , phobia , stress.....etc.
Best is to share it with someone reliable at home and if still unable to handle meet a clinical psychologist in your city.
I feel you need to share to some one actually what you undergo right now and the reasons behind these issues.
Definitely it would help to resolve those issues and face the with more confidence and clarity.
You have not mentioned as to how and when your fear started. But the fact that you are having headache, negative thoughts and disturbed sleep suggest that you might be suffering from depression. The 'fear' you talk about could be the symptom of underlying depression.
You need to consult a psychiatrist, in person, at the earliest.
If you have been abusing alcohol, tobacco and any such stimulant/ depressive substances, I would advise you to immediately stop them, and inform the treating psychiatrist about your habits.