I'm not sure if anyone here knows what causes their own issues, much less yours, but don't fret! Psychology and Psychiatry are different things, and it might be worthwhile for you to see a Psychiatrist. While there is clearly a chemical element to depression, as well as the other problems you mention, there's also a mental one as well, so blood tests won't necessarily reflect that. Having a Psychiatric evaluation will try to get to that. Neurology isn't really what you're after. It mostly deals with how the brain works, not why the brain is doing what it is doing.

My advice is to get to a psychiatrist as soon as you can, and good luck! Keep us posted.