B.B.
There are so many things that can go wrong in the first trimester and you are VERY early along. I would not tell anyone you are interviewing with that you are preggers... But do ask them what precautions they take with pregnant employees in those positions since you are planning on having more children in the future (sooner than they think :-)... With your current employer I would also ask what the precautions are for a preggers employee in that position and what you need to do to fulfill those precautions since there is the "possibility" you may be or will be pregnant.
I would not make any announcements until after your 12 weeks along. (But then again... I am currently 13 weeks with my 4th child and we have never announced BEFORE the 12th week with any of them. We just told our kids last week... And there has been no history of loosing pregnancys neither myself or my family... Just precaution on our part.)
Typically a dr will not "confirm" your pregnancy until you are about 10 weeks. Then they can do an internal ultrasound and see and hear the heart beat to verify. (at least thats what my dr does)
Congrats and good luck with the job hunt!