Low Hcg levels?

I discovered via a digital pregnancy test this morning that i was pregnant. As we have fertility problems and i had a miscarriage exactly a year ago today (Spooky!) We went to get a blood test done which came back as HCG level of 19. I'm on CD28 today and although my average cycle is 28days recently my period has been arriving on CD27. I rekon that the egg must have implanted on Monday( 5days ago) as i had a tiny bit of bleeding. My nurse say's we may have tested to soon or it might not be a viable pregnancy, i am terrified. We've got to go for another blood test on Tuesday. Are these results really bad?