7 Days late but bfn?

Ashley • 23. Married. Expecting #2.
Has anyone been 7 days (or more) late and got a bfn followed by a bfp? I was supposed to get a visit from AF Christmas day but still nothing. I was from Christmas <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> night sick with what I thought was food poisoning (my mother inlaw thinks otherwise) up until day 5 so I thought that may have caused me to be late but I'm really not sure anymore. Day 3 I tested and got a bfn and thought for sure I'd start but I was still sick so I wasn't sure if that'd delay it. Day 6 I was finally feeling better so that morning I tested and still got a bfn. My mother inlaw (she's a nurse) and best friend (she's been in my shoes before) both feel I'm pregnant but now I'm no longer sick, and I don't have any pregnancy symptoms but still no AF. My husband and I conceived in April of this year (2014) but lost it due to a miscarriage in June which was followed with a D&C. We began trying again in the end of August and have since been trying and waiting. We're trying really hard not to get our hopes up but I'm very regular and if I'm ever late it's no more then a day. I'm just hoping there may be someone else who can give me some more insight or personal experience from being in the same boat. I plan to wait it out for another week if I still don't get a bfp and get blood work done unless AF decides to show her nasty face in the mean time.