Should i talk to my doctor if?

i took my medication today, and i'm supposed to eat before i take it, but today i had a few bites of a pop tart. after about an hour my heart was beating at really weird paces. one minute fast, the next minute slow. and it was pounding really hard. my dad said he could see my heart beat through my shirt. i take focalin and clonidine. was it just because i didn't eat enough?