My ecg report is concerning? Of this?

I am 26 years old and would like to discuss some symptoms that have been bothering me for a long time. Recently I had an ECG. While it was being recorded, the staff looked at the monitor several times, looked at me, and asked my age. When I told them I was 26, they seemed surprised. Later, when the doctor reviewed the ECG, he initially looked concerned but then told me not to worry and said the ECG looked more like an old man's. The report was ultimately marked as normal, but this comment has made me concerned. And Something I want to ask that I ahve Low stamina and poor exercise tolerance. I breathe very fast during exercise and my heart beats very fast... Sometimes I experience a brief blackout or near-blackout sensation lasting 2–3 seconds. And recently I got a test and there I saw this my fasting plasma glucose: about 105 mg/dL. Should I worry about any of this ? Or any test that I need to do for more knowledge for my condition, i attach my ecg reports here..