Need help! Low HCG

Sorry it's long! First pregnancy and scared to death I'm losing it. My last period was Oct 26th got a positive November 27th and blood test Nov 29th. I'm considered high risk as I had cancer earlier this year so I seen an OB right away. It was early and we both knew that but he said getting an ultrasound was fine but warned me we might not see anything. I should have been 6 weeks according to the app but nothing was seen in the uterus no sac no nothing so he said maybe I'm earlier than we think. He had my hormone level checked the day after the ultrasound which was Dec 7th and the hormone was only at 344. It was checked Dec 10th and it was only at 444. He said I was most likely going to lose the baby or it was in my tube, mind you I had no pain and no bleeding. Had an appointment the next day and he said it was best to do a D&C so after crying the whole appointment I decided to do it 2 days later. After getting to work that day my gut was telling me to get another ultrasound so I did the next day and they seen something in my uterus! They wanted my level checked right away and it had went up to 592 in 2 days. He brought me back in for another appointment and said he's 99.9% sure it's not gonna survive and that whatever they saw on the ultrasound was most likely not gonna turn into a gestational sac but said he was ok with waiting it out and seeing what happens. Had my level checked yesterday the 17th and it only went up to 676 in 4 days 😭. I just need to know if I'm doomed or maybe there is hope!