Assuming that in your attempts to get your wifi working you have installed the recommended driver (bcmwl-kernel-source) and not tried anything else, this is what I suggest you try.
With a ethernet cable plugged in open a terminal and
Do not reboot because occasionally this removes the wired driver as well.
sudo apt-get purge bcmwl-kernel-source
Now in the terminal
When that has finished should bring the wifi to life. If it works a reboot will make the changes permanent.
sudo apt-get install b43-fwcutter firmware-b43-installer
If it does not work we shall try something else.