slow growth slow heartbeat

Hello.  I am 28 and this is my first pregnancy.  I had an IUI on 9/26.  I had several positive home pregnancy tests, and my bloodwork on 10/16 and 10/19 showed my hCG and progesterone rising normally.  However, at my 6wk 2d ultrasound (10/26), the baby measured 6wk0d and the doctor couldn't see a flicker or isolate a heartbeat.  A second ultrasound at 6wk6d (10/30) showed that the baby still measured 6wk0d, and that its heartbeat was around 65.  
The doctor said that it was unlikely that the baby would survive, and now I am in the process of waiting a full week before going back for another ultrasound.  However, I still have all my early pregnancy signs - bone-deep exhaustion, nausea (increasing in frequency), waking up during the night to pee... I keep trying to see these as signs that maybe the baby just implanted late and will be growing happily by the end of this week, but I'm not sure what the odds are on that.  
Has anyone had early ultrasounds that indicated that the baby wasn't growing, but continued on to term?  Or, alternatively, have technically miscarried but continue to have pregnancy symptoms (and how long it lasts)?  

I find waiting this week to be longer than waiting for my missed period to tell me that I was pregnant in the first place!

[AnnieBrooke]

I have not had the first situation you asked about (early u/s indicating the baby wasn't growing but it was) but I did have the second (a pregnancy that failed but I still had pregnancy symptoms) and this lasted 4 weeks.  The doctor explained that early pregnancy symptoms come largely from the placenta, not the embryo, and the placenta is a separate organ with its own timeline.  In my case, the pregnancy failed (no heartbeat at 9 weeks) and it was 4 weeks before I passed anything.  In the meantime, the placenta was working fine and I had all the symptoms.  Sorry that is not good news for your situation.  I'll hope you just had a late implant and everything is all right.

[stephrus]

I am in a similar situation and the waiting is excruciating!!  By my LMP, I should be 8w1d, but I had an u/s 2 days ago that placed the pregnancy at 5w4d.  The dr said the prognosis was very poor, but not completely hopeless.  She has seen in her career 2 or 3 times when the baby surprised everyone and just grew slower than average.  I can barely function, this not knowing is driving me insane!  I lost my pregnancy symptoms a week ago, but they seem to be making a comeback the last couple of days so I just don't know what to think.  I have to go back for another u/s in 2 days and I'm PRAYING that something will have changed.  I have been obsessively scouring the internet and have found lots of instances that go either way.

Good luck to you and I pray that you pregnancy will progress!!