Officially freaking out 😢

I was schedule for my first ultrasound yesterday 2/15 according to my last period I should be 5 weeks 3 days as of yesterday my HCG levels came back last week at 2404 which doctor told me it was normal but now according to yesterday's ultrasound they see a baby but it only measure 2mm and there is no heart beat but we weren't expecting one since its to early for that. They want to repeat another ultrasound in a week to see if the baby is growing and if they can see a heart beat at that point. I asked her if that was a normal size and she just told me it could mean I'm not as far along as they though I was or may had ovulated later in the month but if I had any spotting or cramps to call them. I feel terrible and this waiting game is no joke.