I was just reading the Mayo clinic page on migraines, because this one has been going on for a week today and I'm sick of it. One of the things it says is that they're caused by a serotonin weirdness, probably the opposite one from depression, or as I've long thought, the migraine blowouts I get may be what keeps me cheerful. Anyway, they mention serotonin and estrogen and chocolate as being connected, so maybe your body is sending you a timed self-medication message?