Hi Sarah,
I think it was really courageous of you to go to a gym class after so many years and I also think that it sounds as if the instructor handled the situation very badly. I'm no fitness expert but I think you need to build up your fitness a bit before you start classes, unless they are very gentle. Swimming is great for that and so is walking. Swimming is also good for your asthma. If they have a pool they probably do Water aerobics, this is a great way to start building your fitness also. Good luck and don't give up but I would work up to the classes slowly. Wendy.