Why do the arches of my feet always hurt? I'm a 42 year old female

Stretching. The most common reason for pain on the bottom of the feet is from the ligament that attaches to the heel bone. Factors that may contribute are weight, shoes, other medical problems like diabetes or peripheral vascular disease. A full biomechanical workup should be done by a professional to rule out this cause.
Stress. I am not sure of your weight or habits. The bottom of your feet have a spring like ligament that springs your foot up after pressing it down when walking. This sometimes is strained too much. Wt loss and arch supports are the first line of treatment.