Thanks for choosing health care magic for posting your query.
I have gone through your question in detail.
Some people do experience what you are experiencing and this is not very common.The common reasons behind this is that if you develop anxiety
disorder then you caffeine tolerance will reduce. Secondly if you are on any medications like OCPs or any other drug that interferes with caffeine metabolism
then it may occur.
Hope I am able to answer your concerns.
If you have any further query, I would be glad to help you.
In future if you wish to contact me directly, you can use the below mentioned link:
Wish you good health,
Dr. Srikanth Reddy M.D.