Advice from Men and Women in relatipnship

Me & my girlfriend . We both been in a relationship for '3 years'. She is the love of my life, Both of our families agreed on our marriage. We might settle by next year. The problem is, throughout this time, i had to tolerate so much. I know i am the male person, and i must handle her pampers and stuffs, i do. But the thing is, when she is having her period days, Those 7 days become hellish for me. She ruins all the good energy without any reason all suddenly. Yesterday we had spent a very good day. She randomly without any reason behaved bad with me,( dry texting, sounding rude) . its not new. It has always been like this. But now as iam growing, there are some things that also bother me in day to day life,. I want to know from men, how do you handle your Girl's mood swings? Like how to stay calm and not loose your cool. And for women, How do you want to get treated? When i ask my girlfriend what's wrong 100 times, she replies nothing 100 times. But i know there is a problem.