Left shoulder, elbow, wrist pain/discomfort after carrying heavy bags or walking dog ? hurts starting in shoulder blade. uncomfortable.

Myofascial : This sounds like you may be experiencing a myofascial trigger point; this irritation of muscle groups can even mimic nerve root type pain. The shoulder girdle area is a common site for these types of regional muscle fiber strains. If your dog takes you for the walk (with lots of tugging) then a few trips to dog training school may help to change unruly tugging. A lighter, fashionista bag ?