You need to go see your doctor, if you cant face telling him then write your feelings down you need to get help for this.
The reason that you feel like this is unknown to you at the moment but when you get the help you need you will be able to work through it and get it sorted.
Please please please go and get help, its not healthy to feel so low and thats why it is an illness.You can get better, we all can, dont let this thing beat you.
Starr