With pain in head, left arm, forearm and wrist, the first thing to be ruled out is a heart condition by a 12 lead EKG. Constipation and
gas could be
causing pressure on the heart. The other possibility is compression of the spinal nerves in the cervical spine region. This can happen due to overuse of computers, work involving straining of neck, herniated disc, canal stenosis, bone disease, spondylosis, poor posture etc. A MRI of the cervical spine and nerve conduction studies may be required.