I can really relate to you except I'm a little older. I think some of this is innate personality traits mixed with deeply rooted behavior patterns. Like I can't change my personality to be a golden retriever happy-go-lucky girl boss type. But I can slowly modify my behaviors which over time can make your mood better and lift your self esteem. I'd say the younger you are while you seriously try to turn your life around, the better, it only gets harder to pull yourself out of a slump as time continues to pass & bury you deeper. Sorry I don't have better advice, but it's really tough, life is hard & there's not many shortcuts besides putting in the work. I live a life similar to yours, except I force myself to do hobbies which I've been doing long enough now that I do enjoy it & overall enjoy life more. Also make yourself go outside & exercise. Leverage things that you like as a reward system for reaching mini goals.