when i found out i was pregnant a week before christmas 2008, i told everyone the next day. then in february i had to have a d&c for a missed miscarriage. =/
i got pregnant again a month a half later and am now 12 1/2 weeks =) yay! this time i kind of staggered telling people. i told my 3 siblings all within the first week of me finding out. i said something to my mom around 8 weeks. and i didnt tell my dad until about 2 weeks ago. i didnt want to tell anyone, this time. but i couldnt help it.
if i were you, i would tell the closest people to you as soon as you want. the rest, wait until you have confirmation of a baby with a heartbeat. if you lose the baby before the other people know, then it wont be as bad because that is less people to tell.. and the people you are telling are definitely going to be there for you because they are the closest and most supportive people you know. this is just my opinion though.