I'm 18 too, and I've had horrible cramps for 7 years of
menstruation.
Motrin doesn't do anything, I don't know why you bother, midol is almost decent, but if you have really bad cramps it's not good enough. The only thing I've found to work, which sucks in the summer cuz it's hella hot anyways, is a
heating pad. I don't take medicine unless I'm practically dying, but for years I was on birth control simply to control my cramping. Ask your doctor about it, if you are interested, it does help. Besides that, You can lay on a heating pad, it's the only all natural way I know of, besides those remedies that taste nasty and are hella expensive.
Also they say potassium helps, but I eat bananas almost every morning, never done anything for my cramping. lol