pregnancy or miscarriage

i took a pregnancy test that came out positive.  i go to my doctor to confirm.  Later that night i go to the hospital with some mild abdomen pains the doctor then took  a pregnancy test, ultrasound and blood work.  Nothin on ultrasound, pregnancy test came back positve and blood work cameback with an hcg levelof 25.  i then took apregnancy test at home a day later and it came back negative.  i have not had anymore abdominal pains since that night which was 3 days ago and still i have no bleeding can you help.