Your arm pit pain and shoulder blade pain can be due to two possibilities;
1) Pinched nerve in the neck; causing radiculopathy symptoms. These symptoms comes off and on (waxing-waning) and can be of varying intensity. Physical therapy, chiropractic manipulation, acupuncture, deep electrotherapy (iontophoresis, phonophoresis), mild massage, local analgesic creams and anti-inflammatory analgesics are beneficial.
2) Myofascial trigger points; This can be associated with degenerative disc disease in neck causing pinched nerves. Trigger points may develop after an initial injury to muscle fibers. This injury may be a noticeable traumatic event or repetitive microtrauma to the muscles. The trigger point causes pain and stress in the muscle or muscle fiber. Myofascial trigger point is a hyperirritable spot, usually within a taut band of skeletal muscle or in the muscle fascia which is painful on compression. The treatment is almost above as following;
1) passive stretching of the affected muscle after application of sprayed vapocoolant
2) physical therapy
3) deep electrotherapy; iontophoresis, phonophoresis, short wave diathermy, electrical stimulation
4) local analgesic patch / ointment / spray
5) anti-inflammatory analgesics; Ibuprofen (Motrin / Advil)
6) ischemic compression therapy; pressure on the points
8) steroid shots
Please feel free for your follow up questions.