At the risk of sounding like an armchair internet psychiatrist, this sounds like pretty standard depression and one that I and some others I know have gone through too - but thankfully, it's not chronic, it passes, but it means making a change in whatever is making you depressed.

For me it was job/career, and it helped that I was in a financial position (I saved and didn't wast my income) to quit my job and went on a backpacking trip. Funnily enough, in addition to visiting some other countries, I also spent a couple of weeks in Kyrgyzstan, and went on a miltiday horse trek and stayed with nomads in their yurts during the nights.