Late period

Keren

Ladies I am 7 days late today I take pregnancy test but they all come out negative and I also did a blood test on Wednesday and it came out negative could I be pregnant even though they come out negative my HCG is at a 9 and was told it needs to be at a 10 for it to be positive and was advised to go retest in a few days but don’t know how long I should wait before going back