HOw long have you had these feelings. I would suggest that you go to the doc. One question I am always asked if there is a family history so they obviously assume there is a link.
Your doc will prob ask you a few questions like... how long have you felt like it, do you have thoughts of self harm or suicide and how often. They will prob give you a questionnaire to fill in. Well I was.
Your best thing to do is go to your doc though and see if he can help you.