Menstrual Pain - Quick Solution

Ibuprofen, Midol, Tylenol, just ask your local pharmacist.

Otherwise, make sure you have a good diet high in vegetables, get enough calcium, exercise regularly, do not eat animal products which came from hormone treated animals (eat organic meat), etc.
Otherwise, just keep the meds handy for the first day

You can get Therma Care heating pads that you can wear under your clothes. They are not noticeable, and the heat provides relief. Take some ibuprofen or Midol. Drink plenty of water, and try to avoid caffeine (it makes cramps worse).

If you are at school or anywhere else that you are not home, try taking ibuprofin or tylenol. If you are home, use a heating pad or take a hot bath. Heat works miracles for cramps.