Late with no positives.

I am officially a week late today. I've never been this late before. Had one really faint positive a couple days ago with a first response but nothing at all since. How long should I wait to have a blood test done? I just hate being in this middle ground not knowing if I should be preparing to tell my fiance, starting vitamins and avoiding cigarette smoke(his), or just keeping on with my every day life. 😕