Hcg @12dpo?

Hi ladies. I had my HCG quant drawn yesterday at 12dpo which came back at 18. I got a vvvvvvfp the evening of 10dpo. I go tomorrow to have a follow up hcg test done to make sure levels are doubling. Does 18 seem way too low for 12dpo, or am I stressing myself out for nothing? Yes, I know I should be asking a dr, I was just curious if anyone has any similar stories or advice in the meantime. Thanks in advance.