Ate 3 hours ago, had an empty feeling in stomach cant really tell if its a belly ache. i just turned 13 2 months ago, is my appetite changing?

well you are most likely growing which means that you may need to eat slightly more to  not have an appetite

the more fit you are, the faster the recovery. your heart rate drops most sharply in the first minute after you stop exercising; it should then fall about 20 beats a minute—a drop of less than 12 beats a minute is considered abnormal. this “recovery heart rate” is measured as part of an exercise stress test.