Blighted Ovum (Anembryonic Pregnancy)

Hello everyone! I know its a very sensitive topic and Im sorry its gonna be a long and (TMI) post. So me and my husband tried to conceived June during my ovulation as per my tracking app and the first day of my last period was June 15.We conceive June 18 and 19 however when I tried to do pregnancy test July 8 it was negative. So we just tried to have sex again the same day. After that i missed my period which supposed to happen between july 12-14 took a pregnancy test July 14 and it was positive. I cannot believe it and we were so happy. I had my first ultrasound and based on my last period i was 5weeks and 1 day pregnant so we will not see anything yet, she scheduled me on the next 4 weeks and i will be 9 weeks and 1 day pregnant by that time. So today i had my ultrasound and based on my sack i was only 6 weeks pregnant and we cant find a heartbeat.I was so devastated and it felt like the world crashed on me. My ob told me to come back after 1 week to see if their will be any changes as 6 weeks it too early to find a heartbeat,but said don't put my hopes up. I don’t know what to feel. Does anyone experience this and had a positive outcome? Or I should prepare for the worst?