Thank you for your question. Although without being able to examine you I can not offer you the specific advice on diagnosis and treatment that you need, but I would try to provide you some relevant information about your health concern.
Most likely, your arm numbness symptoms may be due to nerve irritation in the cervical (neck) spine or arm because of injury where contact between the edges of the vertebrae can cause nerve pain and subsequently arm numbness. In few people, this pain may be referred and perceived as occurring in the back of head, shoulders, arms or chest, rather than just the neck. Other symptoms may include vertigo, nausea (dizziness) and stiffness can be intermittent. It will be best that you consult a neurologist who would like to prescribe Pain killers, steroid and muscle relaxants. Other treatments could be cervical orthosis such as a soft cervical collar/stiffer neck brace to restrict neck movement if it is originated through cervical problem. Hope this helps.
I'm not a doctor, but it sounds like you have an infection in the lymph system under your right arm, which may be restricting blood flow to your arm when you are laying down.
I'd start with a regular internal medicine doctor.