That's really common with anxiety. I know I've felt that before, especially if I'm getting out of breath doing something.

The only tip i have for you is do not let it stop you! You can do this. Join the football team. Think of a good phrase you can say to yourself when you're exercising and get those feelings, like "I'm strong and getting stronger." Or "i am healthy and having fun."

Not as recommended, but if that doesn't help, sometimes you need to get a bit angry with the anxiety, you know?