Can ultrasound detect pregnancy at this stage?

We have done 2 HPTs, one BETA-HCG test (on 3rd day) and one Serum-HCG test (on 5th day). All tests have been negative and this is 8th day from my wife's due date. She is having no symptoms of periods coming like past. BETA-HCG test was quantitative and detected vey low HCG 0.329 mIU/ml. Now doctor has suggested us to go for ultrasound. Do you know what kind of ultrasound is usually conducted at this stage? And can ultrasound detect pregnancy when HCG tests could not? Anyone with such an experience ...