Age21, male. Get chest pain that goes when sitting down after lifting weights / running. Had ecg, 24h holter, exercise stress test, echo. All normal?

Gene SNP analysis. Do a gene snp analysis will help you understand vo2max status - if you want listen to my lecture http://drbrown.Us i explained in detail what would be the benefit of this test.
Musculoskeletal pain. Your pain is related to your lifting weights and is musculoskeletal in nature .You need to condition yourself and ask a trainer if you need to make some changes they way you lift weights.Or you have to reduce the amount of weight you lift and gradually increase it.
Sounds muscular! With all the tests and your age, it must be weight training related. Muscles tighten after exercise. There are many muscles in the upper chest area that can do this. Take an aleve (naproxen) several hours before working out, and see if improves or lessened.