Abot 9 months ago i had a palpitation attack that lasted 3-2 mins.Doctors did an?

ecg and said nothing was unusual about my heart and diagnosed me with stress. 2 weeks later,i had the same thing which got worse and was brought to hospital again. I was referred to a cardio who did an U/S on my heart and an ECG. The results was fine and said i was absolutely ok. Other symptoms started arising later-on, belching and bloating(especially after the attack and eating) of stomach, heartburn, and just recently, i've been having this giddyness after walking about 10 mins and it makes me feel like i'm loosing balance and swaying forwrd and backwrds.I've also nt been eating well. Howevr,i've nt been having the palps attack for the past few months. I've been to 8 doctors for past 9 mnths and none of them seem to take me seriously as i'm only 19yrs. Howevr, these symptoms are quite disturbing and affects me in my studies and daily life.I always feel very fatigue and feel sleepy.I'v no medical history.Btw, i'm 19yr old male and livin in singapore.let me know if more info is needed