Need some encouragement ...

Hey there ladies. My husband and I have struggled with unexplained infertility. I had an IUI on 8/2 and we finally got our BFP on 8/14. I went in yesterday, 9/5, for my first ultrasound and baby was only measuring 5 weeks 5 days when it should have been 6 weeks 6 days. They were able to see a yolk sac but no fetal pole or heartbeat..the doctor is very concerned and “doesn’t think this is the one”. I go back for another ultrasound next Thursday and if there’s no development my doctor is recommending a d&c. I’m so heartbroken over this and am just wondering if there are any of you who have had similar situations and went on to have a healthy baby?