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Had my first scan on the 16th August and was told I was 12 weeks 5 days gestational age.. When I saw my midwife for the first time I said I thought my last menstrual period was the 21st may but I think I was wrong and it was actually 24th May. Yet when I count 12weeks 5days back from the 16th August it lands on 19th May. Why is this? I slept with someone in the month of may just once roughly about the 14-15th May But I had my period normally and everything was fine. I noticed I was ovulating on the 28th May too and online calculators have suggested i was fertile between the 31st may - 6th june. Why have the dates worked out like this? the sonographer gave me a due date of 23rd february.. Is the baby my current boyfriends as i met him on the 31st may and slept with him everyday until roughly the 7th? Do I count back 10week 5days from august 16th? Please help & Thankyou for readingg x