HCG question

tbean25

I recently found out I am pg.  Only about 4.5 weeks.  I had very slight spotting and went to the ER.  I had a pelvic exam, which the dr said everything looked ok.  Cervix was closed and no sight of anymore blood.  Also I had a blood hcg test and the result was 226.  I had to go today to get another blood test and the result was 178.  Has anyone had this happen and still had a viable pregnancy?  Should I be concerned my numbers aren't doubling?