Positive pregnancy but couldn’t verify via ultrasound today..

I am TTC second child and took a pregnancy test Wednesday and it was positive. I was excited but kind of knew I was Pregnant already so only took one test. My last period was august 8th and I’ve been very tired and out of breath. Today I went to get an ultrasound to confirm pregnancy and they couldn’t find the baby. Blood test pending results. I just took another test and it was positive for pregnancy. Did I go to the doctor too soon? Ghost baby? Just hoping for clarity and hoping I went to doctor too soon. Has this happened to anyone before?