Hi, I understand your concern. The headache you are feeling when moving your head backwards to the left after resuming exercise, these are muscular skeletal pain most probably due to exercise. Taking into account that you ve just started to exercise, the muscles could turn rigid until they will completely get used with being under exercise. The floating, floppy feeling on your right arm could be due to nerve compression on the shoulder joint from being over exercised. Continue taking Panadeine if pain is alleviated. Avoid over exercised. Apply analgesic cream locally. If the symptoms will persist, should consult further with your physician and run x-ray of the spinal cord (cervical region) and x-ray of shoulder joint. Wish fast recovery.