You had a headache, killed it with caffeine, then it came back worse than ever. Could it be because of the caffeine? Sounds like a classic withdrawl symptom, complete with the rush and crash effects of drug dependency. I only ask because I developed exactly the same thing in 2000, except my crash was sleep rather than headaches. An hour after a coffee, I was basically sleepwalking, and I would stave it off with Red Bull, which would cause even more aggressive sleepwalking. Went cold turkey one day and suffered like hell for about 4 weeks (and I was a cranky bastard too), and then started to get back to something resembling normal.