I haven’t been to the doctor but i have low blood pressure. Im very athletic but when i start physical activity i get really weak and almost fall over and feel like im gonna throw up. I have a hard time breathing and a deep cough. When i work out my veins should pop out but they don’t when i feel like this. Could i have heart problems?
Im 16 too so i hope its not too serious.

You need to see a doctor.
This is not normal to have a hard time breathing even during exercise.
It could be many things, but only a doctor can tell you what it is.
Make an appointment today before anything serious happens.