Thick endometrium lining but no gestational sac detected (tmi)

Two days after finding out that I am pregnant... I started having this brown discharge kind of how it would look like before my period starts. It got a bit heavier however there was no cramps that accompanied the spotting. Once I did see brown discharge on the toliet paper,  I completely freaked out and went to the emergency room.  The doctor preformed multiple exams on me including a blood test confirming pregnancy and my hcg level, along with an ultrasound vaginally and one on my belly. The ultrasound tech  did not make things any better by telling me he doesn't see a sac nor a baby. The only thing he could see is that my endometrium lining is really thick. My doctor confirmed my fears of a possible miscarriage by telling me that my  beta level is only at a 564. And for someone who should be five weeks it's kind of low. My cycle for the past few months have been 32-34 days however it isn't rare for me to have a later cycle (35 days+). My thing is according to the glow app, based off when I ovulated I should have been able to at least see a sac by now but they didn't find anything. Should I prepare my self for a miscarriage or could it be that I ovulated later then I expected therefore I am earlier then expected? I'm so sorry for the long post but I am in complete shock and worry. If you have a similar story please share.