Out of breath walking short distances

This probably isn’t the right place to post this and I should probably just go to the doctor😂 But wanted to see if anyone had thoughts first.

I cannot walk up a flight of stairs, to my car from a far away building, to my classes at college, etc. without getting extremely out of breath. I have an inhaler because I went to the doctors about this last year and they thought maybe it was asthma but the inhaler doesn’t do much good. I’m bad about exercising regularly, so am I really just THAT out of shape? I am by no means over weight. I am 5’1 and 100 pounds. 21 years old, never smoked, try and eat healthy, work at a daycare so I’m lifting kids all day. I don’t cough after walking, just feels like an elephant is sitting on my chest!

Any ideas? If I start taking walks daily, will I just build up lung capacity?