Low hcg level

Last week I got my bfp and went to dr they did blood hcg and came out to 52. Seven days later they had me retest because they said the levels were low and it came out to 447. According to my Lmp I should be turning 7 weeks on Sunday so we’re a little stumped. Am I less weeks? I have another hcg test on Monday to make sure numbers are rising but I’m still worried as to what’s going on? Anyone else go thru the same thing?