Positive urine test but negative blood tests

Rebecca • 27🌻, 3 angel babies👼🏼 TTC #1 RAINBOW BABY🌈

So this past 2-3 months I’ve had really weird periods and went into my gp today and got a positive pregnancy test as having a history of miscarriage and ectopics they sent me to my A&E department when they ran bloods they said they where negative anyone had this before and been pregnant or is there any other reason test would be positive and bloods negative?