I am having a hard time being intimate with a real person

...I have sucked so bad at relationships in the past, that my wife feels as if I don't desire her. I want her to so badly believe that my only desire in regards to sex is for her and no one or nothing else. I think part of this stems from the fact that I have been involved with porn & masturbation for so long, I am having a hard time being intimate with a real person, instead of being intimate with objects on a television screen. I don't know what to do sometimes, I just feel like I am struggling uphill with no summit in sight...