tautou wrote:我又觉得似乎没有到看医生的程度

It is harmless to do a checkup.
If you are depressed without an obvious reason for over a week or two, you should consult a doc. Doc, at least a good one, will not necessarily subscribe you antidepression drugs. Most likely he/she will tell you to exercise and drink less. That should give you some kind of reconfirmation.
If you are depressed because of certain problems in life, like work, well, you are just gonna have to find a way to fix that as soon as possible, and see if it helps. Remember, the initial cause doesn't necessarily explain everything later. A depression triggered by a certain cause, might slides into a more serious problem once your brain is thrown off balance. It is unhealthy to be unhappy in the long term. On the other hand, identifying the problem and working on the solution, helps one to feel more confident, more in control and happier, even without solving the problem itself.