How long does caffeine stay in your system?

I have this reaction to caffeine where my heart rate increases and sometimes i get minor chest pains with it. Over the past week i've been drinking a lot of coffee but one day i didn't have any caffeine just a candy bar for a snack, and it still happened, but the next day i had coffee again. Does it take longer to get out of your system when you have it a lot in the course of a week?