Pains in Upper Back & Left Arm

I’m experiencing a dull, constant aching pain in my upper back, left side. It radiates in my shoulder, shoulder blade, left side of my neck, & all the way down my left arm all the way to my fingertips. It isn’t super painful, but it kept me awake pretty much all night. It feels like restless leg syndrome, but in my arm & shoulder.

I called my OB & they recommended going to the ER because it sounds like an issue with my heart. I spoke to my mom & she said it sounds more like a pinched nerve; my husband agrees.

Has anyone experienced this? What was it? What do you recommend?

Tylenol is helping with the pain temporarily, but the pain isn’t 100% gone, just not as irritating.

Thank you!