I found a short sequence of a few yoga poses to be effective in relieving menstrual cramps. Following this practice with a hot herbal bath also helps ease the pain and promotes muscle relaxation.
Start with Downward Facing Dog;
Move into a Camel Pose;
Then Bridge Pose;
Finally, relax in Lotus Pose.
Afterwards, soak for 20 minutes or so in a hot bath with a big sachet of ginger, chamomile & mint.
Enjoy!