Get a job working as a janitor, perhaps for your university. Janitorial work sucks, but you will be functionally relevant to some building's operations. Whatever work gets done there, you would play an important role in that.
Also, whoever works in that building will be less likely to get sick. Sanitation is an important part of public health. Janitors save lives.
Do you want to be important? Do you want to contribute something relevant to society? Do you want to save lives?
Go clean shit. Literally. You'll get used to it. Take it from this janitor and former academic. It's not that bad, really. I've done it myself.
While you're making your decisions, perhaps you should play some video games or watch some movies to get your mind off of your negative self-talk. Clearly you have become trapped in a self-reinforcing pattern of thinking. There is no need to continue to spiral around the same old thoughts all the time.
Be patient with yourself. Let yourself have fun. Take a vacation for a while. Buy a tent and go camping for a few days. Walk down some local hiking trails. Reconnect with nature. Let the birds soothe you with their songs. Your problems will still be there for you to deal with whenever you get around to it.