Is It Possible To Have Miscarriage With No Bleeding?

ok i was subpost to be 8 weeks pregnet when i went in for my 8 week alutrsound my obgyn didnt see a baby just a sack and some flioud he said i could be having a misscarrage in a the same day he had me go to the hosptal and get blood drowed and the same thing for thusday to compair the two blood works when i went back in on thursday he said my levels had droped witch could indcated a misscarrage but he says i should be bleeding and cramping trying to pass the baby but nothing has happened i have a other ultrsaound this coming wesday for a second look i have no signs of a misscarage is there any way that the doctors could be wrong and im just not as far along as they thing