Hi, I Took A Pregnancy Test After My Missed Period

Hi, I took a pregnancy test after my missed period and it was positive. I went to see my gynecologist and one pee test was negative the other one which was a sensitive pregnancy test showed positive. They did an ultrasound and found nothing.
Had a second u/s transviginally they couldn't see nothing again! they did a transabdominal one and they seen a small empty sac. If I'm pregnant I should be about 5 weeks. Should I be worried?