Pregnant weeks before starting new job

I received a job offer for the Federal Government as a General Engineer and accepted it in the first week of October. My last period was Sept 28 and in the midst of packing and moving I got pregnant. My husband and I had been trying for 8-9 months even using Clomid to help me ovulate. Once I received the offer I put tracking my cycle and thoughts of sex aside since this was going to be a move from the West Coast to the North East US. I’m now 7 wks 3 days pregnant and really worried that legally my job can fire me because I do not fall under FMLA. I found out I was pregnant the Friday of orientation on November 2nd. I am going to be 40 yrs old in 3 months so I really think this baby is my last time getting pregnant with as long as we had been trying. When I should tell my boss? What should I say? I really have no clue!

**UPDATE**

Thank you ladies for the advice. I have been stressing about how my job will be effected when I finally disclose the pregnancy. Now that I know that the law is on my side, and I’m not alone in this happening at an awkward time; I’m a lot less stressed. I am now just hoping to keep my stress down so I can remain healthy. I am hoping to hold off till mid January with disclosing since I have had a miscarriage in the past and the last thing I need is the feeling of resentment at work for holding up my future projects.