Wow Shinji...your headache sounds similar to what I had early on. I went to the ER on three separate occasions, also to a nuerologist who ordered MRI's of my head which of course came back negative (and costs me a $1000 deductable...grrr). For the first month or so I had an uneasy feeling in my head which would only go away completely if I lay flat. Sitting was the absolute worst. Standing was ok, but flat made it go away completely.
My own research resulted in my own diagnosis that I had a CSF leak. In fact, when I went to Yale/New Haven ER (the thrid and last time), the neurologists there said that's what it probably was and it repaired itself. Sounds like that's what you had too.
But I was still stuck with the problem of discomfort in my head, and only the left side. Feels like your head is full of cotten. I was the one who figured out I had Lyme after exhausting all other options.
Anytime I exert myself too much I go into 'brain fog'/'zero energy' mode. But this Zithromax has really thrown me for a loop. Just can't seem to get a lot of energy back.
Is your discomfort only in your head? Maybe we should compare notes since we may have started with similar symptoms before being officially diagnosed.