Do Not Have Interest In Sex With Wife. Not Getting Excited. No Erection. Advice?

Doctor, With due respect I wish to state that I am quite fond of rounded female buttocks. Unfortunately, my spouse does not have such buttocks. Whenever I see a woman with big rounded buttocks I feel like touching, cuddling them. I used to get irritated and frustrated. As such, I used to masturbate many times while watching porn or fantasizing. Although, I used to be intimate with my wife, I don't get turned on by her. At present also I am not getting excited by watching big rounded female buttocks in porn videos and hence no erection. My spouse is also of nagging type and never prepare me with any sweet and cozy talk. Therefore, I do not feel the incination to make love to her and it makes me further frustrated and angry. Please advice. Thanking you.