Its weird, when drinking you'd get them all the time but knew what it was (hangover). Sober up and they happen all the time. I get them too but nothing a couple advil can't erase. I think its certainly a withdrawal of something or another, most likely sugar IMO. I will also get them if I miss my morning coffee by sleeping in, so that could be a culprit too if you get them when you don't have a coffee.