Posting for a friend. Two weeks ago she visited the hospital where they thought she had an ectopic pregnancy because they didn’t see a gestational sac on ultrasound. They did a laproscopy and said they seen a sac in the uterus. She followed up with her OB and got repeat blood work and her HCG levels were doubling. They scheduled a follow up ultrasound and still can’t see a sac, but levels are still doubling every day as they are currently at 22,000 Has anyone experienced anything similar? What could be happening?