Cardiac fear. The normal investigations?

I am 28 years old and have been experiencing chest tightness, heaviness, and chest pain for a long time. These symptoms do not occur only during exercise. Sometimes they happen even when I am sitting or resting. The pain can be in the middle of the chest or on the left side, lasts a few seconds, and then goes away. Sometimes it is associated with left arm pain, sometimes not. I have had multiple TMTs and Echocardiograms over the years, all normal. CT Coronary Angiography done 3 years ago was normal. My latest TMT (2 months ago) was normal, and my latest Echo (3 months ago) was normal with EF 72%. Today I walked on a treadmill for 15 minutes (4.2 km/h, incline 3.5 for 6 min and incline 5 for 6 min). My heart rate reached 148 bpm, but I had no chest pain during exercise. Does this symptom pattern sound more cardiac or non-cardiac in nature considering the normal investigations? Can I feel it's non cardiac without repeating any tests now please suggest I am scared to the core