What do i have to do so that my wife will not get pregnant?

In order for your wife not to get pregnant you will need to use a condom every time you have sex. Or ask her if she is willing to take Birth Control pills.

FYI: The pull out method does not work so you can also rule it out.

Or you could man up & do the right thing & get a Vasectomy, that will lift the burden from her & put you in control!