Hcg levels dropped

Bertha
I went to Dr at 4 weeks 5 days transvaginal us showed no sac or baby hcg levels were 1261... Then two days later 5 weeks 1 day hcg levels 983... I have an appointment on Thursday for another us and drs appt but im so worried... Is it possible for hcg levels to rise again or is it a miscarriage? If anyone has gone through this please let me know ur success stories, ur support is greatly appreciated!