You should seek a psychologist, and he will definitely diagnose you if you really have depression. Everyone goes through a phase were you feel that you're depressed, but I'm reality, you're just feeling sad, and this feeling is just for a small period of time, but if you've been feeling like so for couple of months, then there is a great chance that you might suffer from another mental illnesses, the psychologist will check your symptoms etc and he will prolly give you the right results.