Better yet, maybe these drs should simply google "ectopic pregnancy diagnosis" as I just did, which brings up this informative document as the first result.
It says "Once referred the definitive investigation is an ultrasound scan"
Be Aware:
Bleeding in early pregnancy - consider an ectopic pregnancy and refer to an early pregnancy unit;
*
Exclusion of ectopic pregnancy cannot be made in the community;
*
Assume a women is pregnant until a pregnancy test is found to be negative;
*
Waiting to see if the symptoms settle can put the woman at great danger by increasing morbidity and mortality;
*
Atypical presentations occur so do not expect bleeding in all cases;
*
Refer if in any doubt for further investigation;
*
Emergency admission is justified because of the potentially serious consequences.
It also mentions elsewhere on the site that before the tube ruptures the ectopic may be diagnosed by blood tests which show that the normal pregnancy hormones are not rising as fast as they should be, so low HCG might well fit the overall picture here.
Of course, as Aitch says, a scan may show nothing. However, if it does and all the symptoms still indicate EP then that calls for a laparoscopy to investigate.
I also agree with blinks that we have only part of the picture. However, if the fuller picture the doctors have includes clinical symptoms of shock then they'd better pull their finger out and do something now.