I dealt with paranoia while pregnant, so if you can calm down, great, but if you can't, don't beat yourself up over it.
In the current economy there are LOTS of situations where people are living with roommates to save money. Unless someone is suing for custody or child support, no one in a position of authority needs to know the details of your living arrangement and who is sleeping with who.
My bf does not live with us, so I don't have quite the same worry, but with two kids of my own I certainly understand how worry about your kid(s) can take over your ENTIRE brain!
I'm sorry you're so stressed, but congratulations!