I HAVE NEVER HAD ISSUES WITH STEPS , I AM NOW HAVING TROUBLE WALKING UP STEPS , WHEN I GET TO THE TOP OF 4 FLIGHTS IT FEELS LIKE AN ELEPHANT IS SITTING ON MY CHEST , I WAS RUNNING UP STEPS A FEW WEEKES AGO, AND THE OTHER DAY I RAN ACROSS THE STREET AND I FELT AGAIN VERY HEAVY IN THE CHEST AND FELT AS IF I WAS GOING TO PASS OUT. I CAN BREATHE , TAKE DEEP BREATHES EASILY WITH NO PAIN IS THIS HEART? OR LUNGS. I HAVE NO PAIN IS ARMS AND I DONT FEEL TIRED