When do I tell my boss I'm pregnant

I just started my job about 2 months ago but my position is not in jeopardy either way. But I'm unsure when I should tell my boss. We have a good rapport and I don't want her to think I was being deceitful by not telling her when we talk everyday and we go to the same places outside of work. I'm 7 weeks now; not experiencing any morning sickness yet just using the bathroom more frequently. But she doesn't see me from her office when I have to leave my desk. Any thoughts?