Do I have atherosclerosis? No one in my family has atherosclerosis, but sometimes I get really dizzy when I stand up. Or if I'm playing sports I can suddenly have a really hard time breathing. Is this atherosclerosis?

No. Your symptoms do not suggest atherosclerosis per se. Your symptoms could be due to several issues such as low blood pressure or dehydration. If you are concerned see your family doctor and have your lipids and cholesterol checked.
It . It may be, but there are many other things that can also cause these symptoms. The probability of it being atherosclerosis depends on many factors, not just your family history. Other factors that influence the risk of atherosclerosis include age, gender, weight, blood pressure, cholesterol, tobacco, alcohol intake, diet, and the presence of other medical conditions. You should see a physician to discuss these symptoms. Your physician may recommend an exercise stress test depending on your assessed risk.