Did i develop caffeine sensitivity?

i think ive become seriously sensitive to cafeine all of a sudden. i usually drink about 1.5-2 cokes a day, but lately, ive been getting really, really bad headaches as soon as i take a sip. i did not notice the sensitvity untill i almost got started on a 3-frappachino-a-week habit, which was early last week. since then i have sworn off the frapps and have been limiting my cokes to only a half a can with my lunch. the headaches seem to be worse when i have an empty stomach or im not eating a 'normal' meal.

the only other thing i can connect with the headaches is that i was supah stressed last week because of exams, but thats never 'conflicted' or affected my caffeine habit before.

help. my coke habit is one of those that im not sure i can ever break and im not sure what ill do with out it.