Actually, "feeling indifferent about everything" is up there on the list of signs of depression. If you're not finding pleasure in activities you usually enjoy, that's one of the larger warning signs.
It's time to talk to a psychiatrist, or at least your doctor. Discuss how you're feeling. The source of the problem could well be emotional: You're unfulfilled at your job, there's something you're not dealing with, or something else. But either way, talk to somebody. There's no reason to feel this way if you don't need to.