How long and often should on participate in strength training activities?
30-40 min, 2-3 times per week, with one day of rest
between workouts
20-30 min, 2-3 times per week, with one day of rest
between workouts
20-30 min, 2-3 times per week, with no rest in
between workouts
50-60 min, 2-3 times per week, with no rest in
between workouts

don't worry, but do consult a doctor.

explanation:

having a high metabolism at age 13 is not abnormal.   however, if you are concerned, do consult a doctor.   the doctor may identify a correctable issue, and then you'll have your answer.   in the meantime, there are a few steps you might consider.

first, reflect on just how much physical activity (work out and dancing) you are getting relative to your caloric intake.   keep in mind that if you are interested in gaining weight, you must have a higher caloric intake than output.   second, if eating robust healthy meals is not providing enough calories, you'll need to include high caloric, yet healthy, snacks.   i warn against using an over the counter high-calorie supplement (drink or food) until you have consulted a doctor.  

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.  

i think its pulmonary not sure tho