Confused

When the scan shows 18-19 weeks, it's just based on a "medical" age. The baby is actually only 16 weeks old or so. "Medical" version adds about 2 weeks allowance to the baby's "actual" age. More importantly, the dating scan is based on the SIZE of the baby. If your baby is fast growing/big size due to parents' genetics, naturally the age will be recorded older than someone else who has a slower growing baby. Dating scan is NOT based on when you had sex / ovulated. Dating scan is only helpful in giving you an ESTIMATED due date. In reality, most people give birth 2 weeks before/after the due date. And there r those who give birth much later and had to be induced etc. Moreover, ultrasound scanning of size of baby can vary depending on baby's position and angle during the scan. For mine, two different scans yielded different age. Nevertheless, doc did not change my EDD by much on the medical record. From the sound of this, there is a good possibility that it's your new bf's baby. Stop scaring yourself or create doubts. Be a happy mummy throughout this pregnancy and enjoy the new bundle of joy to come.