I also don't want to tell my mom i fell uncomfortable talking about it, cause my sister is 13 and she started using a bra in 4th grade and Girls breast development don't yet so it feels uncomfortable when my mom wants to Girls breast development bout it. There is some sort of crusty gunk in my underwear, so is that a vaginal discharge? When should girls start to develop breasts? I thought I had breast cancer. She is only 9!!!