You might also talk to your doctor about alternatives to whatever birth control you are taking now - assuming you are!
Quite a few years ago menstral pain would knock me down for 2-5 days, every freakin month. My doctor and I went through every pill available then, nothing made it better. It was a horrible couple of years. Then we tried Depo provera and bam, perfect. It is not for everyone, but there are many more choices around now than when I went through this so it would be worth checking out.
Yoga is awesome...in addition to the pose above, really learn how to breath as it makes a world of difference in your day to day life, I've found.
If you have a Wii Fit, check out the yoga there ... it measures your centre of gravity while you do poses and I've found it to be an excellent help in making sure I'm keeping the best form I can. We have no yoga instructors in town so this has really been a boon for me.