How is it that I have 4 positive home tests with faint lines but the blood and urine came out…

How is it that I have 4 positive home tests with faint lines but the blood and urine came out negative at the doctors.. This is the second time this has happened to me but last time I only had 2 positives.. Could those tests be wrong from the doctor.. I was even 4 days late on my period then got it for 3 days.. I have a positive hcg test that a positive that you can actually see really good.. I have a follow up with the obgyn on the 4th of next month and they want me to retest in a week..