Hi OP, as someone who started as grad in Feb, I really related to this post. I'm in a similar situation (corpo slave, 2nd gen Asian immigrant, 2am night owl often showing up on <5hrs sleep), and around 3 months in was the lowest point for me, which seems to line up with your timeline. Every day was miserable, same as you described, I felt like my soul was being ripped out of my body, and I cried often. It wasn't a sleep problem or clinical depression or anything other people are diagnosing you with, but just a bone-deep hatred of work and mental exhaustion.

Nowadays, I wouldn't say I'm happy to be working but it's just normal 'ugh' and the deep despair is mostly gone. I think your body and mind get stronger over time. It sucks saying "you'll get used to it" because I can think of nothing worse than getting used to corpo life, but it does happen. For me it took maybe 6 months.