It is possible that it is just too early. How far along are you and are you sure of when you ovulated? Did they ask you to come back later for another ultrasound? With my first pregnancy I was 12 weeks when I got my ultrasound and there was no baby, my doctor said it was a blighted ovum. It never formed. I was devastated but there is a very low chance of it happening again.
Well This happened to me and I was devastated my first ultrasound they kept telling me there is no baby just an empty sac well I did not lose hope 3 weeks later I did another ultrasound and there was a heart beat my doctor said that it was just probably too early. So pray and have hope.
My last pregnancy i was having pains in my abdomen was thought to of been around 7 weeks but went in to er (couldnt see ob til 9 weeks) did vaginal ultrasound but only was a sac. They did the bloodwork and my levels of HCG were really high so i was definately pregnant just not as pregnant as we thought. The baby was not visible until 8 weeks and i was 2 weeks behind the origional calculated due date
It's possible that you ovulated later than you thought. Even with vaginal ultrasound, they won't find a baby before 5.5 weeks, it's just too small. Keep your head up and go in in another 3 weeks, especially as you aren't bleeding or cramping.
Sorry for the typos. My phone is crazy and I didnt proof read!
I had this happen to me with my first pregnancy. We we excited everything felt right and we has positive tests all the way up to the first ultrasound. When we got our first ultrasound it was only a sacred no baby called a "molar pregnancy" my OBGYN of 12yrs stated this is what happens when the DNA does not match up properly to form a baby although your body thinks your pregnant still. We waited 2 weeks and did another ultrasound before our D&C just to be sure.
It's not comforting news but I hope this gives you some answers.
2yrs later we finally got another positive test. We go see the OBGYN on 6/29 and I'm hoping to see a baby in there this time.