The most efficient way is to avoid your period if you have severe menstrual pain. Menstruation isn't always good, especially if you don't want to get kids at the moment and for that reason would need to have your period. A hormonal IUD is very effective to treat menstrual pain longterm and many women are very pleased with that option. Mirena is the most efficient alternative. If you don't want to have hormonal treatment, at least avoid copper IUD since it aggravates menstrual pain. Taking ibuprofen or paracetamol regularly helps against menstrual pain and it's important to take it early (always have it in your purse!) before the pain gets worse. It's easier to prevent the pain at an early stage before it's fully developed.