I was agility training for 3 hours this afternoon, halfway through when swapping dogs i noticed that my right shoulder was a bit achy. I ignored it and carried on- it didnt bother me too much for the rest of the session.
When driving home i became more and more aware of the pain. By the time i got home the pain was beginning to get really bad, its now horrendous, i cant move my arm out in front of me, up to my face or virtually any position really without horrendous sharp stabbing pain shoot right the way down my arm. Even when i keep my arm still, the pain is just throbbing away in/around my shoulder blade.
I had a hot bath to see if that would help but being laid down in the bath made the pain worse. I was actually sick due to the pain...something thats never happened before- i have done myself pretty bad injuries over the years, but this pain tops them all. I just dont know what to do with myself!
Any ideas what it could be/ what i should do?

Oh, and to top it all, my son is now in bed and i have no painkillers and cant go out to get any!!!

Sympathy to you,
my chiropracter told me if you think its muscle injury then you treat it as you would for a strain/sprain. heat pulls more blood to the area and makes it worse, he said best thing is cold pack - frozen peas or similar to reduce inflamation and  any swelling which may be internal and not visible.
I have back problems and cold definatly works better than a hot water bottle.
Chris

Could be a trapped nerve? - see the doc.
I had the same some years ago and was in real agony and it was a Bank Holiday weekend too! Very very unpleasant as there was no position at all that alleviated the pain.
Painkillers from doc and a fortnight's course of Voltarol tabs sorted it, though it did recur 6mths later and now years on I still have a numb patch on one of my fingers (at the time three fingers went partially dead).

Hope you have seen a doctor and are feeling a bit better today qwerty, sounds awful :(

Have a google of 'trigger points' - massaging them hard can be very helpful.  I've been having serious shoulder pain similar to yours for nearly 2 months now - I have somehow damaged a tendon (chronic problem I reckon), the trigger points aren't a cure but they really do help.

The only downside is that the hard massage bluddy hurts!!  But, it does work pretty quickly and eases things off.