What is it about hormonal shift during menstruation that messes up with our minds?

Days before I get my period and during my period as well, I feel it messes up with my mind, I get sensible, down, sad, I cry so easily (my tears just come out of my eyes so easily) I get melancholic and nostalgic, especially since I broke up with my ex around 2 months ago, I get those nostalgic flashbacks and it’s like if they haunted me when I am on my period, I don’t get it!. How can I handle this?