Didn't see the fetus at 5 weeks 5 days

Has anyone had same problem . I went for getting my UTI checked today and doctor also did an ultra sound but could not see the fetus . We just saw the sac and yolk.The doctor says either it could becuases its too early or may be wrong pregnancy . I am really nervous right now . I dont have the next one scheduled until 31. I am also getting my second test for hcg count in blood , hoping it increases.