Measuring behind

I went for my dating scan yesterday was supposed to be 7 weeks 7 days. The scan showed 5 weeks and 6 days so 2 weeks behind. Had a heart rate of 95 and gestational sack was measuring where it should be. I go again next week but I’m so worried. I have had 3 miscarriages in the past. My doctor didn’t seem to worried just said to stay positive that I may have ovulated twice. My lmp was 2/24, surge and IUI on 3/8. On 3/19 I had some cramping. Negative pregnancy test until 14 dpo and it was faint. HCG was 23 on 14 dpo and then 35 48 hours later. The following week it was 445. Does anyone have any similar stories that turned out positive?