What Causes Sudden Chest Tightness, Excessive Sweating And Breathlessness?

When I bend over to work outside or working housecleaning I break out in horrible sweat (not like menopause) my chest tightens up and I can t breathe normally. Sometimes I feel like I will pass out. I have had to lay down in yard to get back to normal and cool off. Then I am fine. It scares me.