Caffeine is always supposed to help with migraines and headaches, actually. In fact, caffeine is found in a lot of headache/migraine medication. It increases the effects of pain meds, also, so if you are taking over the counter pain meds, take them with a coke.

If a person has ADD, that might be different because caffeine works as a depressent instead of a stimulant for people with ADD. I'm not sure, then, how caffeine works in terms of pain management when you have ADD.

Another thing to consider is that (I THINK, not sure on this one) that sugar affects migraines, so if you are being affected negatively by caffeinated drinks, it's probably the sugar rather than the caffeine.

You can get caffeine from other sources w/o sugar. Excedrin and Excedrin migraine both have caffeine in them, for instance.