Nothing wrong with craving BBC. I love sucking my Black Master's cock and crave it when he hasn't called me in a while to suck him. As far as your GF, it depends on how exclusive you are. If you both are still able to see other people, then no big deal if you want to go suck cock. If it's more exclusive, then you can see if she wants to join you or is ok with sharing you with a black man. Other than that, it's your choice.