I have a longer menstrual cycle almost 35-40 days cycle. I had my last menstrual period on August 6th. I'm pregnant. So till date the pregnancy should be 11 weeks but in the ultrasound scan it is measuring to be only 6 weeks with a sac and no heartbeat. Adding to this I have hypothyroidism for which I'm taking medication. What could be the reason the pregnancy is measuring less in age please? Or is it normal to people who have irregular or longer cycle of menstruation? I didn't have any cramping or bleeding till now. Kindly suggest on this. I'm worried. Also on 30th September the gestational sac measured 1.4 cm and then on 6th October it measured 1.6 cm. Had my HCG blood test done and it is around 27829.2 mIU/ml which is in the range expected for 6-8 weeks pregnant.