You may have dysthymia
which is a low grade and persistent depression that makes it difficult to feel really happy or joyful or satisfied with things. It doesn't always get medical attention because it doesn't tend to bring about major crisis. Many people feel like something is missing or they are not connecting the way others do, but as they are able to plod along they can be at a loss as to what, if anything, is wrong.
I have that. It's a pain.
Me, too! Diagnosed at age 43. Nice to finally learn that my problems were not "my fault" but physiological. Just knowing that, added to all the efforts I had been making all along, gave me a boost. Too bad it all coincided with undertreated hypothyroidism--which I am FINALLY seeing an endocrinologist about. He said I should've been treated at a much higher dose FIVE years earlier!!
If you have no purpose in life, make one, no matter how small it may seem to you. I knew an old lady in the neighborhood--her purpose seemed to be walking the area a couple of times a day and clearing the gutters of the leaves blocking them, and telling the same three unfunny, slightly-racist jokes year after year. Yet when she passed, everyone missed her presence as a fixture in the neighborhood.