A few more of my brain cells have logged on, so I just realised that you have what I call "the bear-trap." Once it gets you, it won't let go.
I get one or two a month, with no identifiable trigger.
How well are you sleeping?
When was the last time you had a good, refreshing sleep? Can't remember?
There is a vicious cycle with pain, and one of the most unrecognised is muscle tension. I tend to get very tense in the neck and shoulders, and so the slightest extra stress puts me over the top.
I'm just starting to realise (pain affects the thinking ability) how much my neck and head pains are made worse by this factor.
I'm now taking bigger doses of muscle relaxant at night, as sleep is so important in getting back on top of things.
I was always trying to take nothing or just minimal amounts, but that didn't work.
See if you can get an upper body massage when it has eased off a bit.
You can also do shoulder and neck massages yourself, to just defuse the trigger points.
I'm going to try to remember to do these little massages everyday to stop the muscle tension getting too high.
Daily activities along with constant pain as going to give you huge stress, and you will store this as muscle tension.
Hope this helps.