Measuring ahead?

[lovinmommylife]

So I had my first ultrasound today. According to my lmp I should be 10w5d however, I think that's off. I had multiple negative test, a faint positive on 6/30 and a def positive 7/4. Based off when I believe I ovulated I think I'm 8w3d. I was on birth control so I think it threw off my cycle! Tricky part is my doctor did measurements and said he's comfortable with me being in my 10th week and he's not changing the due date but to me the baby looked so small, smaller than my son did at 8w5d. Anyone else go threw this and it turn out correctly? Note: with my son the ultrasound was done at a specialist office with a better quality machine.