[One thing to note is that my neck and trap muscles are incredibly tight from my backpack,]

Are they often tight like that?

Look up Trigger point info.. you can treat most of them yourself with thumb/hands or a small ball or such against a wall or floor...
Neck, shoulder, pecs, upper chest is also where many nerves & blood flow thru, tight muscles clamping down, adding on the backpack straps pressure can affect those and cause some symptoms..