Need help from girls

I have been broken up over a year, moved on dating someone new. I dont feel the same about my ex and I dont ever want to see him again. (He broke it off w me) However, recently when I get my period I miss him so much and I even cry from flashbacks I get from when we were so in love. Once my period is over and I go cold again not giving a fk about him or his betrayal. I have already mourned the loss and the circumstances, let myself cry, so I know its not pint up emotions.. or is it?? I rarely think about him, unless/except on those days.

What does this mean?? Are those my true feelings? Why does my heart go back to him when I'm on my period? Has anyone else experienced this??

I hate it so much because I'm trying to move on w this new guy and only for those days do I feel like that. It makes me confused as hell.