Am I Sexually seduced?

I am unmarried. I am attracted towards one of my female colleague who is five years elder to me. She is married and mother of two. I enjoy her company. She treats me as her brother. But I am not reciprocating it. I intend to see her sexual cuts each time I converse with her. I try hard to over come this habit, but fail. I even masturbate in nights thinking of her. Am I okay or am I seduced. What will be the repercussion, if I advance sexually towards her?