Pregnancy?

I did a test recently because I felt strange, my period didn't come either and last month my periods were very light and short. The morning test showed positive straight away but at the gynecologist's all the tests were negative. Then the person at reception said I should come back on Friday. Then we did another test which was negative again. I can't shake the feeling that I'm pregnant and then I asked the gynecologist to do a vaginal ultrasound, which she didn't want to do at first. She did the test but after less than a few seconds she said no, there's nothing there, they're not pregnant and she didn't want to look any further. Could it be that I am pregnant and they're just wrong because my whole body is saying yes and now I don't know what to think, it's my second pregnancy and it feels like my first pregnancy.