24 years old and having chest pains, heart palps and left arm hurts. blood pressure is always fine though. what causes this?

Not sure: Your age rules heavily against coronary disease although I have very rarely seen it in a young person. Do you have risk factors? More likely this is something more benign such as anxiety or pericarditis, but chest and left arm pain should never be ignored. See a doctor, get an ekg.

Evaluate further: Multiple possibilites exist. This should be evaluated by a physician to make sure the blood pressure is accurate, the physical exam is normal, and ECG is normal . Other investigations may include holter monitoring and echocardiography. Possibilites include a benign musculoskeletal condition, thoracic outlet syndrome, aberrant coronary artery, mitral valve prolapse, pericarditis, etc.