I think i'm depressed , i feel that i'm sad most of the time and feel like i want to live but have nothing to live for. i feel empty inside .

Depression: Sounds like you are correct. This will benefit from a visit with your doc and may benefit from medication.

Sad: First have a complete physical with a Primary Care Physician to rule out any underlying illness that may be causing these feelings. If you are not ill, then it would be good to consult with a Clinical Psychologist for psychotherapy to feel better and you may want to add medication from a Psychiatrist.