The worstPeriod cramps

One the first day of my period my cramps are the worst. Prescription Vicodin does nothing to help. It's agonizing. The pain starts in my hips then spreads to my legs and feels like I have the worst charlie horses in my legs. Then it goes away no more cramps it lasts about 14 hours but I noticed it's like a cycle. Been in the er a few times for it. Been to the doctor and they want to prescribe birth control but we are ttc so I don't want to get on it just yet. Does any one eles experience this. Or know what this is please help!