How Serious A Medical Condition Is Abnormal Heart Beat In Fourth Chamber?

Hi, I m a 28 year old healthy male that is very active, I ve been in the military for the last 8 years, I m 5 9 and 205 pounds and 18% body fat. Lately I ve been feeling like my heart is beating so fast that it s about to burst from my chest, and it s been like this for the last few days, so much that I fear falling asleep sometimes. I ve had an EKG and bloodwork done but I was told that there is nothing wrong other than an abnormal heart beat in the fourth chamber but that it was nothing to worry about. This is becoming very distressful to me and I ve noticed myself becoming more tense around my family due to this fact