Strengthen anterior neck.
Stretch pec major/ minor.
Strengthen low and mid trap.
Stretch sub occipitals.
Upper cross syndrome happens from maintaining a forward head and rounded shoulder position for hours on end.
In order to reverse this we need to stretch the chest and anterior shoulder.
Then we need to stretch the muscles at the base of the stuff where the neck attaches called the sub occipitals.
Then we need to restrengthen the weakened muscles including the deep neck flexors.
And the low and mid traps that oppose the scapular position caused by tight pecs.
Hit these areas and I know it will help you reduce that stubborn neck pain.