Measuring 2-3 weeks behind

Hi ladies, so I got my positive test on August 28. I KNOW for a fact that we conceived on August 15, and I ovulated August 17/18. Here’s the problem...

I went for my first ultrasound on September 15. I should have been 6/7 weeks, but we only saw a gestational sac measuring 5 weeks.

My next scan was this last Monday October 4. I was supposed to be 8/9 weeks, but we only saw a yolk sac, fetal pole, with a baby measuring 6 weeks 3 days. So in 2 weeks, baby only grew a little over one week. The heart rate was also concerning to the doctor because it was only 73bpm. The doctor said he wants to see me on Monday for another scan, but that he believes the baby formed with a chromosomal abnormality and that the heart will slow down and stop in about a week or two.

I have left this in God’s hands, and if we are meant to miscarry, we are prepared for the worst. However, we are now worried that baby will continue to develop with an abnormality. Has anyone experienced this before? I would love to hear your outcomes/experiences.