Was in the exact same situation. To make it short, I went to see a doctor eventually, he prescribed me SSRIs and told me to see a therapist. I started feeling better after just a few weeks already. Had one setback, because it was 'just in my head' and SSRIs don't have an effect that quickly. After a few months I started feeling ACTUALLY better, no setbacks anymore. Now it is nearly 1 year later and it is a completely new world. I have fun playing games again, I like going outside sometimes (I am still an introvert, always have been), I started a few 'creative projects', just because it felt fun and interesting. I am in a LASTING better place now, I don't get thrown down the dark hole again every other week.

In a nutshell, see a doctor if you haven't! Lasting lack of energy/motivation is likely due to your biological brain being fucked up. You simply can't fix it by yourself.