<human>: My girlfriend (F22) and I (M21) have been in a relationship for over 5 years now and she truly hates porn as a medium for masturbation. For as long as we have been together she has expressed a disliking for pornography, she thinks that it is a form of cheating. I have never argued with her on this subject as I didn't want to make thinks awkward between us. 

The issue has risen since we moved out together into our own home it has become increasingly difficult to masturbate in private. We rarely have any physical intimacy due to her having a medical condition which causes her great pain if we have sex. Due to lack of sex I masturbate regularly while watching porn. I don't want to upset her by the fact that I do watch porn so I would prefer I tell her the truth before she catches me in the act.

So I would like advice on how I should broach the topic and not create any friction between us.

Condense the text into a few key points
<bot>: How do I tell my girlfriend I watch porn when I masturbate, without rocking the boat, while keeping her trust.