It does sound reminiscent of depression, but depression can be chronic or episodic. Just because you've been given a diagnostic label doesn't mean the way you're feeling has to be a permanent thing. I find it can actually be useful for researching how to stop feeling this way. Now you have a word to search when looking for things that can help bring you out of this pattern of thoughts/feelings. You don't have to let the label define you or hold you to this way of being. Many people come out of depressions.