Measuring behind

Had my first scan this past week. I should have been exactly 7 weeks. I track and confirm ovulation with strips and temps. Baby measured 5w6d and we could see a tiny flicker of a heartbeat but couldn’t hear it. I had a miscarriage back in October at 6+1 and I’m so scared baby is not developing properly and it will happen again. Has this happened to anyone else and the pregnancy been okay? Not talking about cases of late ovulation as I had a confirmed ovulation on cd13.