Feel very sad & restless. A consultant?

I am a Healthcare professional working in a pharmaceutical company in CNS brand management. I understand Psychiatry and Neurology as a subject due to my profession. I work without any hassles in work, but I don't feel happy about anything. I purposely try to become social but always feel left out and alone. I start crying on small small things and then continue crying with too much agony felt in stomach and chest, then I couldn't stop crying for long. During the day I feel less energetic and less interest in doing things although I do them. Once in 2-3 months I feel happy and normal. Do I have any problem or i try an correlate with the knowledge of my profession.Should I take advise from a consultant?