Measuring ahead

Hi ladies, I'm really hoping to get some advise and anyone who has experienced something similar, I'm 24 weeks 1 day and I went to the hospital for midwife appointment at 23 weeks and they said I'm measuring 6 weeks further along but all bubs scans show measuring according to what I am. What does this mean, the dr has said nothing but the hospital have booked me additional ultrasound and doubled my appointments