Does Absence Of Foetal Sac Indicate Miscarriage?

I had a normal period on january 3 and on February 6 had a period but it was more like clear slimy discharge with little blood took a pregnancy test at the hospital on march 9 and it came back positive took two home pregnancy test one om march 10 and one a week later both positive started spotting last night march 25 and weny in for ultrasound this morning. Both pelvic and vaginal ultrasound showed no sac. What does this mean?