My husband and I used an OPK. We did the BD each day before/during/after the surge. I’m fairly certain of the date we conceived within 2-3 days. At our 8 week scan, baby measured about 4 days earlier than I expected. As the pregnancy has gone on, baby is measuring bigger and bigger. He’s been measuring 2.5 weeks ahead since our 20 week scan. Is it possible that my due date is wrong even though we used an OPK? Or is baby just big? It makes me nervous as we’re nearing our due date because I do not want to go into labor early if I can help it, but I want to be prepared!