Okay so I was told on a ultrasound scan the baby measured 5+6 but from my lmp(07/25/2017) I should've been at 4+6 basically a week off. What could that mean? Did I ovulate sooner? I had sex the 8th and 9th. I have 36 Day cycles and I was pretty sure the first ultrasound didn't see anything bc I was only about 3 weeks bc the first time they didn't see anything at all and now the baby is measuring 5+6?? Can ultrasound scans be a tad bit wrong?