Ultra sound-empty sac measuring at 7 weeks

Hello everyone, this is my first time being pregnant and I am so clueless about what to expect with anything!

I just had my first ultra sound today ( my app states that I am 8 weeks exactly today). When I got the ultra sound my sac measured in at 7 weeks.. and it was completely empty.

I am trying to process this.. as I believe I should be seeing something in there by now. But I don’t know. Does anyone have any experience or advice for this? I’ve felt super pregnant this entire time.. I am trying to remain positive but now I am thinking I will have a blighted ovum and eventually miscarry 🥺