Welcome to HCM.
Most likely it is congestive dysmenorrhoea. Some persons have pain for the first two days of period. It is said that if the mother has dysmenorrhoea then the daughter will also have it. For this antispasmodic analgesic
such as Cyclopam
tab. may be taken if the pain is unbearable. However let me caution you that all analgesics have side effects and are best avoided. It should be taken only if the pain is so severe that you cannot bear it.
If the pain persists through out the duration of blood flow, then you will need an ultrasound
scan to rule out endometriosis
Wish you all the best.