I'm at my wits end as to what this can be, but my DP will not see a gp.
He gets this thing where it begins with a headache, and then he gets what he calls "stuck in a loop of thought" where he thinks about the same thing over and over and it can be any sort of stupid thought like how to tie a shoelace over and over step by step, repeating the same part of a daydream over and over.
This in turn makes the headache worse and then eventually he starts vomiting which can last anywhere from three- four times in a few hours, to an entire day.
I'm emetophobic and it can't go on with me sitting downstairs at stupid o clock in the morning shaking and sweating waiting for the inevitable sound or constantly worrying about when it's going to flare up again.