Im sorry things are getting more difficult for you. I have trouble walking as well and found that using a rollator so i can sit and rest as needed has been helpful. Take it slowly, rest when you need to, and stay very hydrated

Physical therapy has helped improve my endurance a lot. I mean, there's still a firm cap at 10 minutes, but I can usually make it up to that point without symptoms. I use a motorized scooter to get around. It's important to incorporate walking into your day, but it can be helpful to have an aid while in stores or at parks