Having My Niece's... oh god... My Period!

As I sat in the bathroom eyeing a tampon I was thinking how I can’t believe my niece swapped bodies with me just as I was going on vacation! Now I’m stuck having to act like I’m my sister’s nineteen-year-old daughter while she lives it up in my body… AND I just started having her… oh god… MY period! Damnit, I can’t believe I have to put this thing inside me!
My sister, who believes I'm really her daughter, calls to me from outside the bathroom, “SWEETIE? Are you okay in there? I know your periods are difficult…”
“You have no idea how hard it is being me, MOM!” I have her cramps, my body is flooded with all her hormones, and I'm a man for god's sake, but I'm going to have to use these all week!
Of course, I didn’t know at the time, but having her period meant the magic was broken and we were going to be stuck as each other for the rest of our lives!