Hello. I first want to say congratulations on your pregnancy! That's awesome and my fingers are crossed for you that it all works out! I would connect with your OB. They may do another transvaginal ultrasound on you as well as measure your HCG. If your HCG is still low, there is a chance that you are pregnant but not as far along a you think. This did happen to me. I thought I knew exactly when I conceived but everything was off by about a week--- I ovulated a week later than I thought. It happens! If your HCG is in the range of 1500 to 2000, they typically can see the gestational sac. Many women who have ectopic pregnancies do so by chance and it doesn't reoccur unless you have something anatomically going on or a blockage. So, the odds are that an ectopic wouldn't reoccur for you. 60 to 70 percent of women who have an ectopic pregnancy have a normal pregnancy after (so most).
So, your next step is to call your OB, get an HCG test and have another ultrasound. Let us know how it goes!! hugs
It sounds like you may have just missed your next period which would make you 4 weeks pregnant and about 2 weeks past conception. It is still to early to see anything with an ultrasound. You should have serial HCGs drawn instead and then a sac should be visible at 5 weeks by transvaginal ultrasound. Good luck and congratulations. :)