Bad Thoughts!

I am 31year old female, mother of a 3 year old & a working woman. I have a love marriage. Due to the job we live separately. He comes home at regular intervals. My M.I.L is staying with me and my nephew & niece for their higher studies. We both are active in bed. But somehow I am unsatisfied with him. But still I only love him. I never thought of anyone else except him. But now I am feeling guilty. I think I am getting attracted to my nephew who turned 17 last month. He was like a school going boy to me before turning 17. Now he looks like a 22 year old handsome man with a masculine body. He is roaming bare body in front of me. Maybe that's the reason I am attracted to him. Even I am dreaming of him in bed. His behaviour towards me also changed. He spends time with me, helps me in cooking. His attitude towards me is a little bit confusing .l also want to spend time with him. Even if someday he tries to come close to me I can't control myself. l know i will go in hell for these kinds of thoughts. But please help me how can l change my mind from these seductive thoughts.