ive been drinking coffee since i was a child, i went on to energy drinks and then to caffeine pills, regularly do about 300 to 400mg a day and have once done 600mg, which can be a lethal dose for people with caffeine sensitivity.

it sounds like you have caffeine sensitivity so make sure to be careful and dont go past your limit. (´ー` )

my "worst" experience was with an energy drink which contain ephedra in the 00s, in those days it was not as regulated of a substance and it was in a few brands. I was up for 2 days and felt on the verge of a heart attack throughout, sweating to death, dancing to gabber. i look back on it fondly (´￢` )