Measuring small?

Hi all, looking for similar experiences...I went for an early ultrasound today and was told that the baby is measuring smaller than the doctor would expect and that at this point it’s neither “good nor bad”. According to my LMP I am 7w6d, but I believe according to when I actually ovulated I’m closer to 7w3 or 4d. The baby measured 6w1d today and no heartbeat detected yet (I know it can be too early for that at 6 weeks). Is it possible that I ovulated or that baby implanted later than usual? Looking for answers. Thanks!