so I missed my period May 20th and I had eye surgery May 21 (I was one day late) and they took my blood for pregnancy test and it came out negative. 8 days later I still hadn't got my period so I took a test at home and it was positive. I'm curious why it came out negative? I was only 3 weeks so I'm guessing the hcg level wasn't in my system yet but 6/7 days later it was? it's confusing!