Discomfort in chest& Back. Or anxiety?

Hello Doctors, I've frequent discomfort in chest and upper back. It is also present in left shoulders and arms rarely. It's a feeling of dull pain & soreness. The pain/discomfort comes and goes away. Also, I feel the palpitations at times and I've a resting heart rate of 88-92 BPM while sitting. I got all the cardiac evaluation done. 2D ECHO with Colour Doppler, 3 ECGs, TMT everything normal. I'm obese person and my LDL is 5 mg greater than the normal limit. Cardiologist told that it'll come down with diet. I'm now regularly exercising and controlling my food. Could you please confirm if this is still heart related or anxiety? I'm 25 years old male and do not smoke or drink. I do NOT have any family history of heart problems. I fear of heart attacks every single day.