Any advice?

Hi ladies!

I wanted to give you a little bit of my story to see if anyone has ever expirenced this. I took a home pregnancy test last Thursday Aug. 10th, it came back pregnant. I immediately called my OB to get my HCG levels checked (she wanted to watch me closely because of a previous miscarriage) it came back a 77 on Friday aug 11th. I went back Monday and my results came back as a 64. I know that any kind of dropping is not good. Based on my last period I would be 5 weeks and 5 days when I took the HCG tests. So I went in for an early transvaginal ultrasound yesterday Aug 17th to see if a sac was able to be seen. Well unfortunately there was no sac, she also told me she looked for signs of an ectopic pregnancy and didn't see any signs at all. She told me my ovaries looked good and my uterus lining was very thick. (That is probably because I've been taking progesterone since I have very low numbers).

So today Friday Aug 18th I woke and when I wiped I had some brown spotting on my toilet paper (same as when I had my previous miscarriage)

I know my chances of this being a healthy viable pregnancy is pretty much out the door. I am just looking to see if anyone knows why I haven't bled as of yet and why there was no sac to be seen. My OB thinks I may be having a chemical pregnancy but I read with a chemical pregnancy you bleed before you miss your period & I am wayyyy past my period due date.

My previous miscarriage, we seen a sac and a heart beat before I lost the baby. I am just very confused and looking for some answers.

Thanks y'all!