still a negative over the counter test

hello....
I had an embryo transfer on 7/18.  I had my hcg blood/pregnancy test eleven days later.  It came back as 42.  The doctor said all is ok and I was pregnant.  My second blood test two days later my hcg was 74.7.  They still said all was ok.  Today, just for the heck of it, I took a home pregnancy test and the results are negative.  Does anyone know what this means?  Can an over the counter urine test still not be picking up the Hcg in my urine?    I am expecting this may mean the pregnancy is not viable.  I have an ultra sound appointment tomorrow.  Can anyone help?

[Heather5]

How long ago did you get the 74.7 number? Home pregnancy tests are very different when it comes to sensitivity, so if your last HCG blood test was done recently, and you used a home test that won't show a positive until 150 HCG, that could definitely be the answer. Good luck tomorrow!

[tina1111]

Also, blood results are more accurate. Some women take a long time to build enough in the urine to show on a hpt. If taken after drinking, the urine will be diluted as well. What brand are you using? I would try a more sensitive test like 1st response. Good luck :)  Heather is right, some need at least 150 to show pos.

[ssm511]

thanks for the responses.  heather, i got the 74.7 last week july 30th.  i have not had a blood test since then.  tina.... i used a "first response" test.