so i’m confused

i got positive pregnancy tests thursday, brown discharge thursday / friday went to my ob who said it was old blood and nothing to worry about but also my urine pregnancy in the office came up negative (could have totally been diluted urine)- she sent me for blood work for hcg levels and progesterone - hcg was 72.9 and progesterone was 14 - why are my tests still negative at home ?? do we think chemical?? going back tomorrow morning for blood work to see if my hcg doubled😅🤞🏻