Ok....So i was just lying in my bed listening a song nd then suddenly i felt a strange feeling in my chest it's so hard to explain that but it was like A VERY SINKING FEELING WITH IMPENDING DOOM for just 3 seconds idk it was palpitations or not it's just felt like "My heart is gonna stop" or im gonna stop breathing.... that feeling left me worrying abt my health now I'm in WHAT IF THOUGHTS 
I had 2 ECGS they were normal so it's not related to heart my therapist told me maybe it's due to my stomach or whatever :(
P.S i have GAD