I read an article the other day which asserts that a person's brain is actually altered after watching porn. That it literally changes the shape and makeup of your brain! I have no idea if this is scientifically sound--I haven't looked up the actual study--but it was a fascinating read nonetheless.
I agree that it changes a relationship and the images are impossible to get outta your head, once they are there. I am not anti-porn per se, but it is not for me. Too easy to get hooked on..too accessible and enticing.
Intimacy is hard for me and that would only make it worse. Therefore, I've made a conscious decision to stay away from it. Plus, I happen to also agree with the Church's stance and it feels good to go along with it.