low hcg hospital and tests

So I had a bit of bleeding today and cramping. I went to a&e just in case. They did a pregnancy test and they said it was negative. But I done 7 digital and home pregnancy tests. All came back positive ( before I went hospital) 
They done some blood work. And phoned with results and said it was low hcg and to return back next Friday to get another test. What does this mean? I'm very scared. Am I just implanting? My period was meant to be due 5 days ago