6 week ultasound two sac empty

I had a misscariage 9/21 and a d and c.  I became pregnant 11/13..  I went in for a ultrasound because I had some brown spotting.  Ultrasound at 3 weeks looked good.  Had a hcg test and my
Results was 20,000.  At 5 weeks had another ultrasound and seen possibly two sacs.  Went in at 6 weeks and seen two sacs.  First sac that we only seen in the beginning is empty and dosent look good.  Second sac is empty but my dr said it looks good.  But it looks like its maybe 4 weeks.  Is this possible?  He said, maybe I ovulated twice.  At this point I dont know what to think?  I'm tryi g to be positive.  Since I went to the dr and found out this new I don't feel pregnant.  Not sure if it's in my head.  I'm not having any bleeding or cramping.  If anyone has gone through this

[Dr. Kokil Mathur]

Hi!
It is quite possible that one sac was missed on the first ultrasound. I suggest you repeat the blood HCG levels to see if they have dropped, remain the same or are rising.  Rising levels indicate pregnancy. A trans-vaginal or through vagina, ultrasound should be repeated at 8 weeks to see the progress. The fetus may develop, or it can be a blighted ovum or sac without baby, if the HCG levels are not rising. Take care!