Not everyone is a people person, but all humans have social needs. Do you have friends? Are you and your family close?You mention uni, gym, extracurriculars. How much do you interact with your classmates, gymmates, clubmates?

If your social needs are met: do you have a sense of purpose right now? Some depressions arise (depression arising sounds like an oxymoron lol) from the lack of purpose. The universe is meaningless, but individuals can lead meaningful, happy lives if they have a sense of purpose. Do you have hobbies that are pleasant to engage in in solitude? You can take online courses, sign up to Meetups, learn an instrument, use the Wag app to walk other people's dogs (and earn money!), volunteer, read, write.

If you are already busy and have a sense of purpose: do you maybe just really miss being loved, hugged, held? Not everyone can be happy single, and if you're not among the few that belong to that rare group, you might have to admit that to yourself (that you need love), put yourself out there and start looking among your peers or on OKCupid.

Lastly, are you eating and sleeping well? Our physiology underlies our moods to an underappreciated extent. Could you be deficient in EFAs (Omega 3, 6), Vitamin D, Magnesium? These are crucial for, among other things, mood stability and cognitive function. Due to the great nutrient collapse (all food losing nutritional value due to soil depletion) even the healthiest eaters today are deficient in Iron, Omega 3, Zinc or some other micronutrients.

Please feel free to PM. When I was 20, I was very busy and "productive", but sad af at night in the solitude of my room.