Anyone else!?

So, I had been getting extremely faint lines for over a week now, we a few stronger positives. I was driving myself crazy and ended up going some where to get an ultrasound done. She said she couldn’t find the sac yet but my endometrium is very thick, so saying I most likely am definitely pregnant just very early. Has this happened to anyone else? I lost my baby boy at 16 weeks a few months ago.