Ok this is a stupid question so I’ve namechanged but I really needed advice!
I live in an area with nice scenic routes and am looking to start jogging/running to get fitter, but I physically can’t do it. Everyone else seems to go out jogging without any problems but I’ve always been rubbish at it! Even as a child, I could sprint fast and would win 100m races, but I couldn’t and can’t do any sort of distance running without collapsing with exhaustion.
I can’t run for more than 20 seconds without being so out of breath and feeling sick that I have to stop. I feel like I physically can’t breathe and that someone is sitting on top of my chest and my legs go like jelly. My BMI is in the very low 20s so I’m not huge, but I really want to be able to run for fitness and just to tone up.
do people build it up gradually, is there any recommended programs or breathing techniques? I’ve been trying to slow my breathing when running but it seems to have no effect and I end up breathless anyway. I’ve watched YouTube videos but still can’t do it. How do people run for miles without stopping to walk?!

For context, I have a blue inhaler for seasonal allergies and wheeziness but I’m not asthmatic.
Any advice or help would be amazing !!!