Positive hpt but negative blood test

Queen

Ladies,

I have done an hpt test at 6 dpo and got a faint line not very faint but faint and pink.tested negative on 7,8,9 and 10 dpo- tested again at 12 dpo and got a vfl and again today with 3 different brands and got a faint line in all 3-i went for a blood test and it was negative below 1iu.did this happen to anyone? I have a tiny bit of spotting.