Yes, communication is vital. You both need to define what the limits of the relationship are, and be open to the possibility that those limits may change over time. You don't have to feel guilty about your thoughts & feelings. I have noticed that when you are bi, the "focus" of your orientation can shift over time, so don't stress out about that too much. Just define your commitment to each other, and be supportive of each other. My own bi partner shifts back & forth between being interested exclusively in women and being into men. We roll with it.