If i used the same shower sponge on my body when i had my last vaginal yeast infection. should i have changed it to prevent recurrent infection? if i should change it in future should i change right after last dose of yeast infection medication?

You do not need to change a new one, just soaking it with a diluted bleach solution then rinsing well or put the damp sponge in microwave for one minute and that should be enough to kill the yeast.

Body sponge will not affect your yeast infection.

The hot water kills the yeast infection, but for peace of mind, buy a bunch of sponges. Bacteria and fungus can grow on wet or moist sponges, buy more and throw away used sponges.