Hi Naenig . what you're describing is by 90% the way i used to be about 6 years ago . things started for me when i was 16 and kept getting worse despite my several psychiatrist visits . then finally i got into analytic therapy and though progress was very slow , with the help from my family , i managed to get over some of the bad things that had been going on . just like you , i felt extremely worthless and although i was in pain , i constantly scolded myself for being sad and useless cause on the outside , i had what it takes to be happy. i don't suggest you necessarily get into analytic therapy , but you do need to seek professional help . also , since you mentioned living with your parents , i guess they're supportive and you could reach out to them .
i haven't had an official diagnosis but now looking back i think i had depression and your condition sounds like depression too .
i hope you find the right therapy and feel better soon .