I hate this!

L.
Why am I so emotional? My bf thinks I've lost my mind. I'm on the 4th day of my period and I yell at my bf then I feel sorry and cry and apologize then I'm mad and yelling not 10 mins later.  I feel like I'm losing it!! Is this normal or do I need to go to the doctor and get some meds to calm me down? 
I truly just don't understand my emotions right now and I need some advise.