Still can't find anything :(

Samia
Today I had done another ultrasound..Doctor can't find anything still not even a gestational sac yet!!...By the Lmp of mine it was 7-12 dec...Now i am almost 6/4weeks pregnant..But i am too worried,for this...I need a suggestion...Should I worry for this or wait for 9weeks?...i am so panicked for this... :( ...