"Having a boyfriend that isn't honest with you and that manipulates your reality is painful and causes women to feel increasingly distrustful. Sometimes that distrust manifests itself in security and clinging behaviors, which the man can use as FURTHER justification to avoid telling you the truth."
-
http://goarticles.com/article/My-Boyfriend-Has-a-Female-Friend-From-His-Past...Should-I-Be-Concerned-that-He-Refuses-to-Introduce-Me/817905/