Repost: dad picks on me about my period.............?

when I get frustrated he says things like "are you on your period or something" and one time I was hiding my underwear from everyone (im very modest) and he yelled "Is that personals?".My mom tells him to stop but he doesnt.Im gonna be 14 next month.I feel kind of babyish asking how to stop it but it really embarreses me.So what would you do?