Talk to Gynecologist on Menstrual Cycle / Periods

Its my first day of periods, i have some cramps but a deep pain pelvis and towards belly button. I suddenly gets pain in abdomen and feel dizzy, my heartbeat slows down and my bp drops. It happened two times today with 5 hours gap almost. I eat some sweet, get rest and drink water then i feel better. I am kinda worried, what is this? Is it normal ? Please guide me