sac but no embryo

Diana • 33 trying for my rainbow baby

so I've been having brown discharge for 2 weeks already. I was having some period like cramps and went to the er. they did the basics. urine, blood, and also did an ultrasound. well they found a sac but no embryo. It measured at 5 weeks 5 days but I should be 6 weeks 6 days according to first day of last period which was 12/15 unless I ovulated late. so now I have an appointment with the ob tomorrow. I also have multiple uterine fibroids biggest is 5.4 cm. anyone have something similiar and how did it and up?

UPDATE: went in today for 8 week ultrasound and nothing there. an empty sac still measuring at 6 weeks like I was two weeks ago. Dr said the sac is abnormal and it's a missed miscarriage. im having a D&C; tomorrow. my heart is broken. I thought this was my rainbow, but looks like it's our second angel now 😢😢