I am 21 male, about 320 lbs. I get a sudden thump in my chest with a small squeeze, and I get out of breath. It usually lasts 1-3 seconds but its really scary, I usually reach for my chest when it happens. It can occur at any time, but I noticed when I am more active it happens more frequent. It occurs often when I bend down to pick up something.It can happen twice a day, or once a month. I went to the doctor and he took a echo cardiograph of my heart, and it came out good. I do suffer from anxiety and have been under a lot of stress lately.