Sadness and depression are not the same thing
Why Depression and Sadness Are not the Same | World of Psychology

Some people with bipolar think they have depression. I can't and won't try to give you a dx of what you are suffering from but you are saying that you have lost an enthusiasm for life and that is a sign of either depression or bipolar.

Can you give up on doing all your favorite things and lack an interest in life and not be depressed? Maybe the question could be how can I get out of the doldrums?