there are many things it can be, most likely just stress
related. you said youre 19 so i assume you're eithe rin college or probably just started a job. i know everyone says this, but u should go to a doctor and get an ekg. the exact same thing happens to me. i went to the doctor and within a few months i had an implanted defribrilator. dont mean to scare you or anything because it really is probably nothing, but getting it checked out cant hurt.