Baby measuring smaller/ bleeding

Natalie • Married 11/14/15. 4 children. Mom of twins.
Has anyone experienced a pregnancy where you had bleeding and the baby was measuring smaller than expected? My LMP puts me at 7 weeks tomorrow, but my baby is measuring closer to 4-5 weeks. Baby's heart rate is steady. Doctor is calling it a threatened miscarriage and ordered bed and pelvic rest for now. I'm hopeful but also prepared. Just wondering if anyone has had a similar experience.