My HCG very low and not doubling

SM
So I'm 5 weeks and 1 day pregnant. I had a miscarriage last month and got pregnant again right away (doctor said my mc was very early on and I was okay to try again right away). Finally got in to do my bloodwork and my levels are very low. Friday at 55. And Monday at 77. I'm not spotting or bleeding or anything. I'm in range according to the nurse, but on the very very low end and not doubling like they are supposed to. Should I prepare for the worst??? I'm such a wreck right now!!!