Seconding the suggestion to see a mental health professional about your mental state.

Saying that I’m dead inside doesn’t seem fitting, it sounds too negatively connotated. I just got nothing inside, it feels like. I just do stuff in autopilot, not feeling anything about it in any way. In retrospect I don’t know when the last time was that I sincerely laughed about something or was really sad or angry about stuff, it seems like I just go auto-pretend in order to act appropriately or look interesting to others.

This sounds a lot like how I experienced depression at its peak. You may not suspect that you're clinically depressed if you've never really experienced anything else your whole life. Same principle as gender dysphoria.