What Causes Shortness Of Breath While Climbing Stairs?

Dear Dr. Rynne, I took an EKG about a month ago and it was normal. However, I have been having shortness of breath walking up the stairs, exercising my biceps with a 5 lb weight for a few minutes or using the rolling pin to roll pastry dough. I also was diagnosed with a 50% blockage in 2012 in one of my arteries and smaller amounts in the others (no stents). I also have a deviated septum and my nostrils are constantly blocked, especially when doing those activities mentioned above. My two brothers have had 5 bypasses and 4 bypasses when they were in their late fifties and early sixties. My father died of a heart attack at age 45 having two previous ones. Hopefully, it won t cost me anything. Thank you!