Clear blue and first reponse positive ...but

Michaela • Mama to Charlotte Rose 7.30.18💛 👧🏼 Chloe Evelyn 👧🏻 Caroline June 👧🏼11.05.20
Okay I'm so confused . 
Why is it that the expensive tests are postive but the cheap ones are negative ? I would be 6 weeks exactly today ...     I've had a blood test and it was postive but my hcg level was only 12.