Yes as already mentioned we need more info to infer the cause of the problem.
Some possible causes: If there is any compression between the scapular spine and muscle of the affected tissue there will pain. This is called impingement/tear (weakness or certain angles hurt with weakness).... Or degeneration of AC joint also undergoes compression when lying on it and brings on pain.
As a solution a physiotherapist could try taping the shoulder with rigid tape and that could alleviate some pain.
Next Steps
icing reduces the inflammation. 15 mins wrapped with towel and 3 times per day.
you need an assessment for further treatment options as it is hard to know what we are treating.
Health Tips
try to avoid lifting and if there is no option, lift close to the body. If you are exercising in the gym avoid lifting, pulling, pushing with the upper limbs completely!!!