Hi I Went To Doc When I Got To Know

hi
I went to doc when i got to know about pregnancy then doc told me for ultrasound to find out whether there is any ectopic pregnancy but it shows only intrautrine pregnancy and it was almost 6 weeks
I had an abortion 4weeks ago and had an ultrasound after 10 days which showed complete abortion but after 4 weeks i had an pregnancy test which shows faint line . what this means?