Bilateral upper arm pain without injury?

I have a raft of chronic pain/rheumatic conditions incl fibromyalgia, lupus and myofascial pain syndrome, but this particular problem is new and isn't fitting the pattern for any of those conditions which I've had for a long time, and know plenty about, so trying to figure out other possible causes. I apparently do have a single trigger point in my upper R arm, but while the pain of that was localised and caused bone pain too, again, what I'm suffering now is different in that it's both upper arms, and feels almost as if I'd pulled or torn the muscles really badly and continuously yet I've not lifted anything heavy (at least not with both arms), and anti-inflammatories/narcotics (nor anything else!) aren't alleviating the pain. No redness or swelling - just an interminable dull ache that is worse with movement and at its absolute worst on waking in the morning but which eases off after an hour or so to a lesser ache which lasts all day. Any ideas?