I'm anti-pornography. Realistically--as the mother of two sons (one who has masturbated as his major source of comfort since he was a toddler)--I know that masturbation is normal. Pornography is a line-crosser, though. And I DO believe it's a "gateway" to sex addiction.
Unfortunately, I speak as the BW of a man who is a SA. A week after our wedding, while moving into our apartment, I found his last phone bill. It was $800 worth of calls for phone sex. I was hurt but naive. Like someone else on here, I tried to be modern and non-prudish. I believed it was because we weren't together yet and he had needs that had to be fulfilled. I paid the bills and never saw another bill like that, so it seemed a non-issue.
Within our first year of marriage, though, he got a letter from a friend about his old GF getting married. He tried to hide it but I could tell he was upset. That night, he left our bed (which woke me up). When he didn't come back, I got up and found him pleasuring himself to the snowy porn available on our TV. I cried. We were newlyweds; he had a beautiful, loving, available wife in his bed; and he chose that method of escape.
Over the years, I'd catch him looking at photos (usually only that) on the computer. I was crushed. He was in the military; he was away from me for 6 months at a time; he was surrounded by porn in that culture. But I didn't want it tainting our home.
About 7 years ago, he finally went to therapy (for adoption/self-esteem issues/anger issues) and found out he was a SA and a rage addict. For 6 months, we abstained sexually, so that he could dry out. He confessed to me that even when I thought "we" were making love, he was really just--crude, hurtful truth but his words--masturbating inside of me.
So, while he was healing, I was falling apart. I couldn't get past the fact that he'd intentionally hurt my feelings or make me angry so that he could have an excuse to act out. Which made him feel like a jerk. Which started the whole cycle (with many more parts than that) again.
If he was ever sharp or intolerant with the kids that day, I felt like being intimate would be wrong because he'd be acting out with me. I stopped trusting him to know the difference. I didn't want him to look at my body naked--the one that had borne (two c-sections) his four children. I didn't want to be intimate with the lights on. I felt insecure and inferior--although, realistically, I've aged well.
Against this background, he met a young woman in his own field, with a similar mathematical/scientific background, who was in a male-dominated world, who was aggressive, who was in a practically sexless marriage (although 2 children), who'd already had one A. They began texting (he'd always had boundary issues with women, was a compulsive flirter--but in front of me, so I thought it was harmless--and had been asked by me to discontinue several friendships that had become EAs although not called that then), she upped the ante to sexual innuendo, and he was ripe for the fall.
She was his soulmate. She completed him. She accepted his SA and loved him anyway. Until she dropped him (don't know why, exactly).
When that happened, his fantasy world was shattered and he acted out, hooked up with a prostitute locally, then with 2 escorts while on a business trip.
I found the e-mails describing what he wanted with the prostitute (the subject line? "lessons") and when the rendezvous was happening (the day before I found them), then watched $100s vanish from our account while he'd be away.
All of this? Because he has not found acceptable or positive ways to comfort himself aside from porn/sex. It all started with normal, teenage self-pleasuring, progressed through lingerie/swimsuit model photos in high school, phone sex in college, porn magazines in the military, videos while on business trips, computer/TV porn at home, then led to an affair and then even more illicit sex.
So, IMHO, masturbation is "normal," but pornography is toxic. No matter the reason, the porn use, to me, would be a red flag.
I'm so sorry that another woman has to go through the sort of nightmare I have. I wish you well whatever happens.