I usually end up dreaming about this particular person whom I used to talk to. I have feelings for him but decided its best i give him space because i thought he may not be interested since he kind of holds back when it comes to relationship and anything intimate or concerning his feelings. I dreamt once that he told me he is seeing someone else and that he was sorry for leading me on. However, it was just his voice and someone else's face. He called the lady's name who is actually a married woman that i work with.

I am confused as to what that would mean.

I would say that there is the unresolved issue of you having feelings for him. Possibly you're worried about rejection from him which could be why he said he was in a relationship in your dream. Deep down though, you may be realizing that he may not actually turn you down which could explain his voice with someone else's face. His voice may have just been the worry of rejection from him creeping up.