Abnormal ECG. Changes a cause of worry?

Hi im 26 years old couple of months ago i had fever which wore off after one week..a week later suddenly my heart rate went 144 bpm and i felt like some air bubble in my chest i had an ecg done at the time which im attaching. It showed minor st and t wave abnormality. i sometimes experience that episode now and then 2d echo was normal bp is normal i do feel random chest pain for fraction of seconds sometimes on the right side and sometimes on the left. My stomach is also upset and i feel very gassy during these episodes. What is the cause of these ecg changes and also i do not experience any chest pain while jogging or exercising just some random chest pains at rest for fraction of seconds. Im really tensed and no doctor has given me satisfactory answer some say its normal some say it may be due to gas. Please tell me what this is and are those ecg changes a cause of worry? Thank you