Your girlfriend might want you to give him more space because she or a friend are having the affair with your boyfriend (oops, sorry, did you not want to hear that?). It's not very uncommon that different cultures have an underlying lack of respect for each other. Trust your instincts, he doesn't like letting you know what he is doing, so he calls it prying in order to make you feel guilty and discourage you from being in his life (the complete opposite of what someone should want for a close relationship). Maybe your girlfriend or someone she knows is not having a relationship with your boyfriend, maybe they're just giving that kind of advice because they really don't care and would be cheating in their relationship.