period 2 kali sebulan (14 days period in a month)

Hi semua, sis ada period problem since 5 years back.. Dalam sebulan tu biasanya akan kena period 2 kali. First kena 7 hari lepas tu period stop for 1 weeks plus then kena lg period for another 7days. Everytime period mmg sakit because period cramps & back pain kena sekali??.. Dulu doctor pernah prescribe pil utk betulkan period but it didn't help much. Ada tak anyone ada masalah yg sama mcm i? What will do you do ??