What Causes Hot Flashes During Menstrual Cycle?

I have just turned 18 and have had my period for about 7 years now. I have experienced what I believe are hot flashes. Twice in the last 3 months. On the first day of my lunar cycle my lower abdomen would feel bloated and pressured, then around midday I felt dizzy and the super hot. At first pale and then red faced. The heat would be unbearable and would last for a good 10-20 minutes. And I wiuod also feel the need to puke. After this exoerience and near fainting situation, any discomfort in my abdomen disappeares, no more heat or nausea. But then I would get chills and be super cold for approximately an hour and would feel exhausted! My periods have also been irregular with very little flow. I was wondering what the cause if this is and if there is anything to be concerned about?