Sorry for coming in late, but: headaches that start abruptly (as in "four months ago"), are this disruptive, and keep going on for months should be checked out by a doctor.

You moved three time zones in the middle of the problem, and you are not reporting a big change in frequency/severity. This makes random outside factors less likely. While food can be a cause of headaches, it is actually not that frequent of a cause, and usually a clear link can be found - especially if someone gathers extensive data like you did.

If you really want to avoid medical professionals, try washing out your sinuses with saline (Neti pots often work well) once a day for a few weeks - an indolent sinus infection could be a cause. But if this continues (and especially, if it gets to the point of causing nausea), please try to get to a doctor ASAP.