could the er doctor be wrong about my miscarriage?

I was told 2 weeks by an er doctor that I had probably had a miscarriage but I had not experienced any bleeding.There was a sac prsent. Could it be possible that I was not as far alng I as first thought. I took 3 test within2 week of each other. the 1st read negative but the last 2 were positive. I still have not had any bleeding. I did experience some cramping nd twinges. the er doctor said there was signs of a pregnancy. However, the 1st er doctor told me that my HCG levels were low and i certainly could not be as far along as i thought or even pregnant. Like I stated I hav enot any bleeding. My waitline is continuing to expand and still hasve had no bleeding at all- Is is possible that it was too early in the pregnancy to tell. Like I i said the er doctor said it in all likelihood a miscarriage. Could he be wrong?