i am 23 years old, and for the last two weeks or so i have been feeling a sort of pressure feeling in my chest, right in the middle, and i begin to feel very weak and as if i am going to pass out. it onlylast about 4-10 seconds...it isnt painful, just feels weird. i went to emergency and was admitted into the hospital. but nothing showed up when i was there, a few days later it started up again. they did some test at the hospital and nothing showed up. :/ i dont know what to do. what could this be? or what should i do?