If you don't know what to do don't get tensed because that will worsten your situation.You' ll definitely have to do some introspection.
Some suggestions
Is it really the profession you hate or your work place and the people out there?
Do you overstrain yourself?Not keeping time aside for relaxation at all?This might be one of the reasons why you are feeling this way.
What's your hobby?Do you have any?If not try doing something new for funsake.For instance join Dance Classes.This was just an example .You don't really have to do this.Do what you think might be fun for you.
Do you have an exercise regime?I had read somewhere that exercise goes a long way in keeping depression in check.Since then I try my best to exercise regularly and it makes me feel much better about who I am.
Try doing some social service.Nothine can make you more happy than making someone else happy
I hope some of this helps you.But don't give up Ok