why do my feet hurt when I have my period?

I’m going with water retention. If your weight jumps up during your period is can certainly be attributed to water retention. Now add gravity. The water heads south lands in your feet and you get uncomfortable.

Not sure what type “hurt” you mean. maybe if you have lots of endometrial tissue floating around in your abdomen during the right time in your cycle it presses on some nerves? Many people with back pain get pain down their legs and in their feet. Total guess, I am not a doctor.