What Causes Spotting When The Heavy Objects Are Lifted?

Every time i left something heavy i start spoting or bleeding but not heavy bleeding just when i wipe in not to much on my pad in fact i can were a panty liner when it happens. Also if i stand for along time i start cramping realy bad in my legs in stomach as if my monthly was coming but it does not and if i sit down the craming will go away as with the bleeding if i relax off my feet for a day it will stop and go away. What can be causing this