Sac measuring behind. Help!

Kenia β€’ 23πŸ’• πŸ‘¨β€πŸ‘©β€πŸ‘§β€πŸ‘¦πŸ‘ΌπŸΌπŸ•πŸ• After 22 months TTC I miscarried at 7 weeks. TTC after miscarriage πŸ’™πŸ’–

So according to my LMP I should be 7 weeks and 2 days. I had an ultrasound done today and they said I’m measuring 6 weeks and 4 days. We were able to hear a heartbeat. The doctor told me that sometimes that happens and he’d see again in 3 weeks for my official dating scan. Has this happened to anyone before and they went on to have heathy pregnancies? I’m kind of scared. We tried for 22 months and I’m on edge about everything. Should I change my prenatal? Is there anything I could do better?