What does my heart rate tell me?

I woke up this morning, went to school and had been sitting down long enough to get a resting heart rate. i had a vente frappe and drank half of it in about 30 min. next thing i know i'm feeling light headed and just crappy. i check my pulse and its 102 beats per min! I don't normally smoke but had one a couple days back... and i normally drink caffeine like this. i don't know whats wrong. this is the first time this has happened so i don't think i need to go to a doctor... am i suddenly sensitive to caffeine or what?