My fiance and I went to a pregnancy center yesterday to get the first ultrasound on our baby. The nurse said that I was 8 weeks and 2 days along but when she did the ultrasound, it showed that I was 6 weeks and 2 days along. We saw the heartbeat and the baby is about 6 mm long. The lady said it is probably nothing to worry about but this is my first pregnancy and I am only 17. We are very worried. I told the nurse that my periods were irregular and she said that might be the reason why the baby was small. She said that I might ovulate at a different time than expected, making me not as far along as we thought. Please help.