I can only speak from my wife's experience. She had very little in the way of pregnancy symptoms and morning sickness with any of her pregnancies (at ages 32, 34, 37, since you ask). Our babies were girl, boy, girl.
Never, never believe any of that huge number of myths which surround the whole business of sex and conception and the positions in which to have sex for a boy or a girl etc etc. In a small family of 2 or 3 children, or even a large family of 6 or 7, the odds for each child being boy or girl are very close to 50:50, no matter what your experience at any stage during pregnancy.
And your numbers do not tally. 3 months is 12 weeks. What sort of doctor makes mistake like that?