Hcg level

Had my first hcg level done yesterday according to my LMP I would’ve been 3 weeks 4 days yesterday... haven’t “missed my period” yet that would happen on Thursday the 21st... my first HCG was only 13.. the only symptoms I really have is cramping and nausea sometimes after eating... I had an ectopic in February and my HCG level started at 17.. I’m jut terrified that the number is to low I know I have to go back in 48 hours seeing the doctor today.. any success stories would be great 😔