blood tests are accurate, your doctor may do a blood test that monitors her levels, in pregnancy every day certain hormone levels increase with this blood test will show is if her levels are staying the same or raising, if they are staying the same it would mean your not pregnant, if it raises it means you are and things are going well.
now allot of time after a miscarriage you will get positive pregnancy test readings mostly from a home test because of the hormone still being present, this had happened to me after miscarrying before and my want to have a child made me feel like i was still pregnant a month later and having a positive home test and a positive test at the clinic through a urine test, but once they did the test by blood it showed no signs of pregnancy.
it does not sound to me that this is your case you did not mention a previous miscarriage, but what they will probably do is either A. 1 week hormone check "test is done by a simple blood draw", or B a in the clinic mobile ultrasound, this will show if there are signs of early pregnancy for certain, "this will be done with a ultrasound probe inserted into the vagina, there is no pain involved. early pregnancy will not be able to be picked up by the over the stomach"
i hope this helps good luck to you, if it shows you are not pregnant have fun continuing to try