Why I can't have a baby boy and I have 3 girls and im pregnant and they tell me its a girl?

Gender Selection. The chance of a boy or girl with each pregnancy is 50%. The chance of having 4 girls is 6.25%. To get a boy, you need microsort (research and not available now) or ivf/pgd so that the embryos can be genetically tested and the normal girls transferred to uterus. More expensive but virtually 100% successful if you get pregnant. Most centers do not offer so find one that does. Good luck.
It was random. Your chance of your next baby being a boy is 50%. If you find 16 women, each with 4 children, on the average, 1 of them will have 4 boys and 1 of them will have 4 girls.
It's no you. Gender is determined by the gender chromosome the sperm brings to selection.When dad's girl carrying sperm get there first, you get girls.It is ALL dad, not you.You have nothing to do with gender selection.My GGGfather had 10 boys and 2 girls, it just happened that way.Quit beating yourself up over this issue.
Gender Selection. I agree with the math of the gender selection. I would like to add that some ivf centers offer gender selection services. Currently the only way to accomplish gender selection is to use ivf and pgd to biopsy the embryos and find the ones that are male or female and then transfer those. If you become pregnant then it will be the gender you desire. Pgd also checks all the chromosomes. Hope this help.