I think what you are facing is an existential crisis. This often happens to really intelligent people, people who’s intellect exceeds wisdom. Your mind is “smart” enough to question such great things, but you lack the “experience” to link together purpose. This is becoming increasingly common as more people scrutinize life. Unfortunately people just scrutinize and never take a step back to experience. Intillects of the west have seen this problem many times, and what they refer to your “disease” is something called dispair. In existential terms, people go through life creating their own identity. A part of this identity is a career or life purpose. You go through life trying to build up towards some grand purpose (ex- a grand career, a grand relationship, a grand involvement in something). Eventually you may find that your grand purpose was not really something you wanted afterall. Maybe you really wanted to have a successful career, but are finding a job gives you less satsifaction than you thought. When this happens you feel “despair,” a feeling that arises when the identity you work towards is not something you want. Economically this is a “sunken cost,” an investment into something that will not pay off. You may spend much time seeking an answer or seeking some job, but find that is not what you want and then you “despair” over wasting time. The root of this problem is that we at a young age strive for some grand identity and only that identity. What we need to recognize is that there is no grand identity we can conceive of without some sort of “wisdom” (experience). When young with no experience we try to create something that’s not what we want. Instead just try to create multiple identities, and over time you may recognize what this grand identity is. Just live on and it will come to you. You just need the experience to enhance “wisdom”, and this wisdom will alight the seed of grand-identity that you are waiting for. Now this is really painful to just wait idly by for that seed to come, but that is all you can really do. It will grow on it’s own. Don’t despair over wasting time, instead realize that this is growing the seed. Even getting a degree in something you don’t like is still helpful, it still serves to reinforce that is not what you want. Now you can go on and try something new.

Solution? To cope with the above you need a spiritual connection. I don’t mean religion, I mean spirituality. Spirituality is not the same as religion, and although it could involve a deity there are non-deistic spiritual paths. This just means an overall connection- whether that be the cosmos or god, or your own nature. Read a little into Thereveda Buddhism, they deal extensivly with your problem. Try Vipassana meditation. There are religious texts like Inky suggested, but these often just serve the intellect and not the wisdom. The Bhagivad Gita is a good quick read- it is the first text on psychoanalysis. Another figure, Alan Watts, has really good books and youtube discourses that discuss life/death/spirituality/purpose in terms relatable by intellects.

I face the exact same problem you do. I go through bouts of depression over seeing the point of it all, but when I take a step back I see better. Don’t worry if you get depressed over this, it is quite natural. Just remember that overtime things will work out.