I'm A 17 Year Old Girl Currently In High School

I'm a 17 year old girl currently in high school and I'm taking my first physical education class there and it's been awful. I'm not very active, so I expected to be sore, but when we did cardio I couldn't catch my breath for around twenty minutes. I just wanted an opinion on if this is just because I'm out of shape or if it could be something like asthma that I just didn't know about.