just got a new job and pregnant

Lilly
Hi ladies,
So I just landed a job I've always wanted and WAS so excited about it. Reason I say was is now I'm nervous about revealing my pregnancy because I don't know how they will react. I am a motivated and dedicated worker and have excelled in all my previous positions (but they don't know that--or me really, yet). I was only 4 weeks when I interviewed.
I know I will most likely not qualify for very much time off when the baby comes and don't want to lose my dream job but I would want to spend more than 6 weeks with my newborn. I am currently 9 weeks pregnant (and not showing) so there is still quite some time to think about how things will be post partum. 
My main question or what I'd ask you is when did you reveal pregnancy at work? How did the boss react? Any pointers/suggestions? Especially interested if there are any in my position starting a completely new job.
Thanks