I have been an avid coffee drinker for many years now and have never had any bad reactions to it. I began drinking coffee (de-caffeinated) when I was as young as 9 years old, and began drinking caffeinated coffee once or twice a day when I was 14 years old. I am now 22 and do not drink as much as I used to, but still enjoy the occasional cup in the mornings and/or afternoons. However, in the past month or two, I have noticed that almost every time I have a cup of coffee, I experience headaches and nausea about 15-20 min later, ranging from moderate to pretty severe. Sometimes I feel so bad that I must lay down in order to subdue the feelings of nausea and headache. I have always been so tolerant of caffeine/coffee until now, which makes me wonder if I could have possibly developed an allergy or intolerance to the stimulant...I would really appreciate any possible advice or reason as to why this unfortunate situation has occurred.. Thank you.