Thanks for your query.
Pain and numbness you are experiencing along your arm and shoulder is due to muscular spasm caused by overuse, strain (caused by hyperextension neck injury
,sitting at a keyboard for long hours),cervical spondylitis
,electrolyte disturbance or any other internal mass applying pressure.
Some times it can be due to fractured bone,anomalous first rib or cervical rib
which leads to compression of nerves and vessels behind color bone causing pain, numbness, paresthasia, weakness,pallor, cyanosis
You may need to perform chest and cervical spine
x-rays or/and MRI to rule out above mentioned conditions.
Oral muscle relaxants and vitamin supplements may help with your condition.
I advise you to visit concerned doctor for further evaluation.
Hope it helps.