Tests can only confirm a heart problem, no test can rule out a heart problem. Anyone who tells you otherwise is a liar.
There are multiple forms of angina, and "variant angina" can be triggered by stress and anxiety. It also tends to happen at a resting state.
And be careful with doctors, all because a persona is capable of intense study and memory retention does not mean or even imply they have a high IQ or are even competent. I have had the misfortune of running across multiple cardiologists who tried to tell me I was stable and fine though I kept having regular angina and multiple heart attacks at an early age.
If you truly feel something is wrong, and the doctors are simply not investing the proper effort in identifying it, then keep trying with new doctors. It's your life your protecting, don't let others who aren't feeling the sensations of your body try to tell you it's all in your head.
I know when you get a chest pain and read about heart problems, it can worry the hell out of you. Basically you have been tested and found to be normal, great news. You know, at your age, you can make big differences to your heart condition in the future. You've felt the worry now, so imagine what it would be like in the future if you do end up with heart disease. You can just make sure you never smoke, eat healthily, exercise regularly, train yourself to not react so much to stress through relaxation techniques, and keep your blood pressure/cholesterol in normal ranges. Do those things and I doubt if we will ever be speaking on here again :) I wish I could go back thirty years and do that. I've had attacks of very bad angina over the last 4 years and believe me, what you describe is not what happens. So please relax and get your healthy future on track :)
Sorry if I seem a bit brutal in this post, but this is important:
Why on earth do you think you have angina? You wrote: "usually he worries when exercise aggravates the heart, which exercise does not do for me"
If the chest pain doesn't worsen with exercise you do NOT have angina.
You also wrote: " that almost can be described as tight muscle."
If it occur during rest, doesn't worsen with exercise and feels like a tight muscle, the answer is almost certainly that it IS a tight muscle. That happens to all of us from time to time. The same is the case with "skipped" beats. That also happens to everyone from time to time.
I really think you know all the answers to your questions, you just need reassurance. That's OK. The doctors aren't always good at that, they usually just say that you are OK (or not). I think you need to work with your anxiety, it wouldn't surprise me if that's the cause of your problems.
You're already examined by your doctor and if he thinks that you're OK, I would trust that.
I can guarantee you that 100% of us have some occational chest discomfort, but most of us don't pay attention to it.