My sister tested positive with two lines, then had a stomachache and blood clots. She went to the hospital for an HCG test and the result was pregnancy, but the blood clot test showed no pregnancy. Now, she has stopped bleeding, the test still shows two lines, but she had a vaginal ultrasound and a regular ultrasound but still did not see a pregnancy. It has been a month since her period ended last month. So doctor, can you tell me why the test shows two lines but the test shows no pregnancy?