Had history problems fantasizing lot of women and girls

Hi everyone,

Since 2001 when I was 19 years old I started fantasizing a lot about girls and lately about women. I did not put this fantasy in practice against them. Now I am married and devoted but these fantasies are still keeping me on and on, especially dreaming about my wife cousins, sister in laws, acquaintances. Whenever I want to either masturbate or have sex wit my partner, my sis in laws are weakness to me, their great bodies appear and I am down. One of them has grown up and is almost 28, unmarried, but did some things I thought she would never do, dated one married men 12 years older than her, after her termination with that affair, I heard that she has affairs with people that have money and good cars, so I never thought she would do these things. So she was basically a mistress, but now she is dating one bachelor man. My fantasy about her is not over, she notices that I am crazy about her body as we very rarely chat about relationships, ways she deals out with her friends. I am somehow jealous why she did not have affair with a good guy and end with a good marriage but kept going with married man whom she gave everything and he controlled her more than he did to his wife. Their relationship ended with problems because although they loved each other they knew they never marry until they got caught. It appears that this relationship create a different personality in her, becoming very adventurous and open to sex, namely being as crazy as I am for this job. I see her very rarely but she keeps me laid when I see her. She is ten years younger than me and as I explained is horny more than I am. Same about my wife's cousins, they are hot but with failed affairs, we rarely see each other but when we see each other, I notice they like to tease me with words.
I did not do anyone illegal after my marriage but I am desperately in want to do someone just for that instance. I am 37 now and I am aware that in 40s and 50s I will be different but want to use my last chances. I always thought relations within my wife's family would be better and controlled with high intimacy, perhaps knowing some of them and knowing how trustful I am to them. Of course I want very brief relationship (2 months max).

Can you please help me on this>?