Trying to not stress out!

I lost my baby girl in February and it has been very hard for me since then. Well I just found out I am pregnant again and the doctor is watching my levels. I had an ultrasound done at 6w2d based off my lmp and we only seen the sack. She is worried my levels are not doubling and I'm so worried that im going to lose this baby.

Here are my hcg levels

Aug 4th - 18

Aug 6th- 62

Aug 13th- 2481

Aug 20th- 12311

I go for another draw today but I am trying not to stress. Do my levels seem to be okay? I know different doctors say different things but I need some input please!