When I think of how warm your body is, her face comes up in my mind.
When I arouse myself by recalling how your kisses traced on my skin, my brain instantly makes me imagine her face that she is feeling your touch too.
When I am saving my breath at a brisk night so that I won't be quashed by missing you, the scene that you two snuggled in my favorite blanket to warm up together in your room is also reminded.

I feel you are contaminated.
I feel your clothes, your underwears, your bed, your room that you brought her behind my back, your car, your town, the memories we created together with all of these -contaminated.

She is not your "cool" friend. She is a devil wearing a mask of a benevolent person.