Hi, I can empathize with you because I get extremely bad cramps every month. The cramps have been so bad at times that I came pretty close to fainting from the severe pain, many times. But in your case it may have been coupled from not eating all day, and then just eating the honey bun. Meals and snacks are better eaten with some protein added so that you don't have that drop in energy.
I don't think it is your heart since you are only 15 years old it would be very unlikely the cause :)