Nausea, Rapid Heart Beat, Due To Stress??

i m sometimes experiencing nausea, difficulty of breating, my heart beating so fast, lack of energy, my nerve twisting almost everyday..feeling scared sometimes, what could be the reason? is stress can caused this? i m vegetarian, and i experienced weight gain for about 5-6kg in the past 6 mths..ermm i m 24 years old What is Panick attacks?is it serious? is killing? i can feel suddenly my heart like burning..and difficulty in breathing? is this the symptomp? Thanks all for your answers... Additional info, I only feel all that symptomps when i feel scared/too worried...