HCG levels

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Nervous because I went to the doctor on Monday after taking a pregnancy test on Sunday and getting a faint positive. They called me back and said my HCG level is 103. Needless to say, I am freaking out. I believe I am a little over 4 weeks. Date of last period was 12/5.  My sister in law is also pregnant and didn't have any HCG tests. 
I went back today and should get some results tomorrow. They kept on throwing around the term chemical pregnancy yet I've had no bleeding. 
Has anyone else experienced low HCG with a successful pregnancy?