I Love Pretending To Be Extremely Pregnant

Today and maybe tomorrow I will be home alone with my sister and I want to tell her that I pretend I'm pregnant like we used to when we were kids before she leaves for college in a few days. I don't know how to bring it up and I'm kind of scared to do it because of her response and that she might tell someone.

What I'm wishing will happen is that she'll accept it and after seeing me with my belly on and occasionally rub my belly she will decide to pretend with me like when we were kids.

If I do this I will try to get some pictures and maybe even post them on here, but I don't know if it will happen. If anyone has any advice please tell me I could also use that for my grandma who is coming over on the 31st. Thank you in advance.