No baby seen on ultrasound

I'm currently what I thought I was 6 weeks 3 days based on ovulation, I usually ovulate late around cd21-cd23 cycles vary from 33 -35ish days. i had a positive opk on 2nd August. I booked an private early ultrasound tranvaginal, yesterday. Long story short he couldn't see anything anywhere apart from my thick lining. he checked my tubes etc no baby to be seen not even a sack. There was no fluid or any concerns. He said I could just be too early or miscarriage or eptopic but he doesn't think eptopic as I'm all clear. This also happened to me in March but I also had brown bleeding snd cramps but this time I don't have anything. I took a clear blue this morning and it still says 3+ weeks and it hadn't gone down. I'm so upset, I have no idea what's going on, I really thought this was my rainbow baby! has anyone else had this?