Pain/Sensitivity Increases in one area, only after decreases in another area

During my meet prep phases, I tend to get acute flare ups in back pain and also shoulder/neck pain. I’ve noticed that when my back pain subsides to a pain level of 0,1 or 2, my shoulder/neck sensitivity starts to flare up, but it never happens together.

It almost feels like my body limits itself to how much pain it can feel from fatigue/overload. Does this happen clinically or in literature? Is it called something?

I’m not entirely sure what you are asking here but we do have evidence of exercise induced hypoalgesia.