Blighted ovum?

Here’s a little backstory. I went in for blood work last week at what I thought was 6 weeks pregnant. My HCG level came back really low. So I went in for 2 more blood draws, my level wasn’t doubling as the doctor want it to be. Today I went in for an ultrasound. I saw an empty sac. The sac measured 5 weeks and 2 days. I go back in 2 more weeks to see if anything changed. Has anyone else ever experience the same thing and still went on with a full term pregnancy?