You could have several different things going on here. You could have rotator cuff injury, frozen shoulder, pronator syndrome, etc. I would recommend getting evaluated by your MD, as you will need an xray at minimum to see what the problem might be. If the xray shows little and doesn't match your symptoms, an MRI might be needed to rule out a rotator cuff injury. Until you can see your MD, you can try to take an over the counter anti-inflammatory medicine like Ibuprofen (always take any of those with food, as they can cause stomach ulcers) to help with your pain. Good luck!
You do need to make an appointment to see our doctor or see a physiotherapist.
Weakness in the arm and hand can sometimes be referred from problems in the spine.
The other thing to bear in mind is if you do any repetitive work that may have triggered off this problem. If so, you may need to consider to change the way you do things so as not to cause further damage to your hand and arm before you get a proper evaluation and given the appropriate advice and treatment.
sounds like a circulation issue. try messaging it from the shoulder blade, down to the front, and then strongly on the back of the shoulder blade.