What Should I Do If I Have Pregnancy Symptoms And An Expanding Uterine Sac But A Negative Pregnancy Test?

good day i have a little problem and i dont know what to do ... monday this week i went in for an ultrasound i was not feeling good and there was a sac in my uterus then when i went on thuesday the sac had expanded or developed im not sure yet what it is but i have alot of pregnancy signs like bloating i look pregnant i have had a baby before but that was 3 years ago i also have breast tenderness and loss of appitite... i have done a pregnancy test but it shows negative i am so stressed and confused .what should i do please help