Please help me :(

Based on my LMP I am 8weeks 5day but yesterday I went for ultrasound and the doctor said to me that I am 6weeks. Is it normal? I really scared. Doctor told me that I'm pregnant according to the sac shown in ultrasound but the doctor didnt see the embryo yet. He asked me to come again when I'm 10 weeks. But right now I cant think of anything. I am really scared something bad might happen. I really need oppinion :(