It's sounding like a trapped nerve in your neck, this usually gives bad pain in the shoulders.
Suggest ice pack on shoulder, every evening.
Also plenty of the voltoral gel.
Take nurofen befor work
If it's killing you, go docs for stronger pain killers and muscle relaxants.
Make sure you sit upright at home.
Check van seat make sure you use lumber fully out on seat , if no lumber adjustment, use a small cushion at the base of the seat back.
Look at standing back as far as poss when poling upstairs Windows, lightest pole available.
Go to see an osteopath.
I have this condition, I get flare ups, the worst last year lasted over 9 weeks.
It's a tough one.
I feel your pain.....literally
Mr B