31 weeks & not leaking from my boobs ?!

Deb
I have 2 friends that started leaking and starting have colostrum; I'm 31 weeks and 1 day and I haven't had anything yet, my nipples deff changes colors and are darker & there's an ugly vein on top of my breast but no colostrum build up or leakage. Is that normal? 
Sorry for the TMI