bleeding + no sac at 5 weeks

went to A&E to check as I had light bleeding. tested positive in few urine tests and blood test is HCG 75. however, no sac found in ultrascan. i need to go back 48 hours later for another blood test to see if HCG rising. my bleeding became heavier next day, any chance it will be successful pregnancy or most likely will be miscarriage? mummies, please help ease my mind 🫶🏻