How do i know when im going to get my period!?

i know i shudnt be emberassed but all my friends have it. all of them. so dont tell me everyone blossoms at different times because i know! when i jump up and down my boobs hurt really bad and i wear i sze 32a victoria secret bra but i only fit into a pushup and i barely fit into it like my boobs barely fill it up. i have jet black pubic hair but my hair is blonde/brown. My longest strand of pubic hair is a little over an inch. I have discharge but its not like HUGE GLOBS OF THICK stuff. i just have it like alot. Please tell me how long it will be:(