I get sick very often and i was wondering if anyone had an idea why.?

I am a fifteen year old girl who is very active(competitive gymnastics 3 hours 3 times a week and I go to the gym at least twice a week for extra exercise.) And I have been getting sick A LOT. I was sick for a month and a half with strep twice and bronchitis once and every since then, I have been getting sick randomly where i throw up for 12hours then I'm fine. Does anyone know why ????