Arm Pain

I have not been diagnosed with anything. I see a neuro in January. However, a mew symptom has popped up and the past 3 months I have had excruciating pain in my upper left arm that comes on suddenly, last a few days then disapears. When this occurs I basically lose use of the arm from the shoulder down. I can not reach for things, can't use it to lift myself out of bed or off of a chair, driving and dressing are very difficult, I can't wash or style my hair, etc. I opporate more like a baby t-rex, having to keep my arm close to my side, only able to use my forearm. This has happened 5 or 6 times since Sept.,always in the left arm until yesterday when it hit both arms at the same time. The pain was so severe I went to the emergency doctor this evening, however they had no answers and are sending me for an ultrasound. I guess my question is whether anyone else has ever experienced this type of pain, that comes on suddenly, last a few days then goes, only to return. It is definitely muscle pain, not bone. Up until now I haven't had any pain, only strange sensations which cause discomfort.