You might have depression but reading that post I get autism/ADHD more than anything else.
I note that you don’t really describe the sensations and feelings you experience, it’s framed through being ‘unmotivated’ at work. Inability to describe feelings is a classic autistic trait. I could of course be jumping the gun here but it’s definitely something to look into.
Your description of feeling like you’re the only person in the world who experiences stuff this way also remind me a lot of my own experiences with autism and the accounts of others living with it. Communication difficulties and difficulty reaching out are also rolled up with all that too.
Your descriptions of leaving tasks half done, working irregular hours, and getting distracted with something that’s not in the work item are also very common autism/adhd experiences that I see in myself and others.
It’s good that you are getting tested for ADHD - note that autism and ADHD are quite comorbid and it’s very possible you have both.
The good news is that, whether autism/adhd or depression, you are far from alone in your experiences, certainly very far from alone in this field. It does get better.
Where depression came in for me is I had a lot of self hatred about how my brain worked, and h things other people seemed to be able to do easily I had to force myself to do, with immense effort. In a way, depression is anger turned inward, and it’s very easy to be angry at yourself.
It will get better. It’s about learning how your brain works, what your limits are, and what works for you. Basically, self-compassion, because shame is only a short term motivator. It’s so easy to burn out, and so much ‘advice’ online is about pushing yourself more and more when what works is listening to and understanding yourself.