4 wks preg, tested pos 7 days ago, now neg 😩

Lindsey
What is happening? I tested positive 7 days ago, confirmed in dr office 2 days ago. Today I woke up with mild/moderate bleeding with slight pressure/cramping. I just took a pregnancy test and now it's reading negative. Can that happen that quickly? Does this mean I had a miscarriage? I just don't see how the hcg levels could leave my system that quickly.. Help!! 
Update: went to ER this evening, confirmed that I am having / have had a miscarriage. My hcg levels have dropped to 2.49. 😢