Chest Pain, Breathlessness. ECG Shows Inverted T Wave And ST Depression. What Is The Need For Invasive CT Coronary Angiogram?

Hi! I have been having on and off chest pains for a few years now triggered by exertion, lifting, reaching for things beyond my reach, etc. The pain is squeezing, radiating to my left arm and it makes me breathless and progresses so painfully and lasts from 15-30 minutes without any management. I had a few ECGs that were all normal and even my blood investigations showed normal results. I took those pains as just muscular. But last August after trying to get myself to sit onto a concrete fence using both my hands/arms and chest muscles, the same pain started but it got so worst, I felt I could not breath, got clammy and very pale. My friend helped me into a recovery position as I did not look good at all and was going to collapse and eventually passed out. She took my pulses but could not feel any, she has to call an ambulance. When the crew came, I was already back to my senses, I still had like a pain score of 5 over 10. He gave me Aspirin and took a ECG while the pain was still ongoing. The result showed inverted T wave and ST depression. After a few minutes, when the pain was gone, I had another ECG which was normal. But was eventually admitted to the hospital for blood tests and monitoring. Troponin tests and other levels were normal and I got myself discharged as I need to get back home. Now, the cardiologist back home suggested non invasive CT coronary angiogram. The result, I was told, suggests a possibility of narrowing in one of the main coronary arteries. The advise given to me is to have another CT coronary angiogram but the traditional one. Now, this is freaking me out I am 46. I have been very careful with my diet, I don t smoke, I exercise, I love walking too. My big question is, why do I have to go trough another CT, an invasive one at that, when I thought the previous one that I had would give an accurate view if any of my cardiac arteries are blocked or not? Please help me if you can. Thank you so much.