Irregular gestational sac

I had an ultrasound 5 days ago and sac was measuring small and weirdly shaped and had a yolk sac. Ive never had this happen with all 5 of my babies. I figured it was a MMC. I then went back yesterday expecting a bad outcome...but the sac grew, still irregularly shaped, and there is a baby on the left of the yolk sac with a HR of 110. I have another ultrasound tomorrow. I am measuring 6 days behind what i know i should be based on tracking ovulation and when i got a positive test. But what the heck?! Anybody?