I'm a 29 year old female. For about three months I've had this thing where I get a sharp stabbing sudden pain at my left collarbone. It lasts anywhere from 15-45 minutes and can bring me to my knees--I have to stop what I'm doing at work. Sometimes it also shoots up along my neck and behind my ear. This happens 2-3 times a week on average, but sometimes 2-3 times in one day. Twice, when it lasted a rather long time, my shoulder/armpit/upper arm has been very sore the next day as if I had done something strenuous. I have had no injury to that area. I thought it may be from stress initially, but it just keeps coming back. I went to an urgent care clinic (I recently moved and don't have a primary doc), but the doc just massaged my shoulders/neck and gave me some muscle relaxers. That was about two months ago. Neither helped. It just makes me nervous. Any ideas?