So this past weekend I went on my first real backpacking trip (did a short one night trek last year), doing 41 miles over three days/two nights out in Delaware Water Gap. At some point over the course of the weekend I did something to cause some pain in my upper back. Right at the top of my spine kind of where my upper back meets the base of my neck, and the pain is usually triggered when I make a motion where I bend my head forward or reach my arms out in front of me.

My torso size (measured at REI) ia 19.5. I am 5'5" and am carrying a M sized Mariposa 60. I haven't dove to much into calculating my base weight but I estimate my total weight with food and water this weekend was in the 20-25 lb range.

Has anyone experienced pain like this before? Trying to determine what caused it and what maybe I was doing wrong over the weekend. I'm prepping for a PCT thru hike next year, and this was my biggest takeaway from the weekend that I want to address ASAP. I will likely talk to a doctor about it at some point but wanted to gauge the community's experience as well.

Thank you!