Everyone here is MISSING the point. She WANTS more sex, he's not interested, and he's masturbating in the shower when his IN THE FLESH wife is there and is ASKING for more sex. There is an inundation of men (usually is their 20's but not limited to) heading to sex therapists and couples heading to marriage counselling for this type of issue. These men have grown up with unlimited amounts of free porn and used it for stimulation so long that the unrealistic sex and bodies in it create an unrealistic expectation of real life sex. That means real sex isn't a turn on and they start preferring to watch porn and masturbate instead of real sex because real sex isn't so over the top.
Now don't get me wrong. I watch porn and like porn. If I keep turning my husband down I understand he needs release. Go for it. It's when I am always asking for it, ready willing and able, and then see in his history feed he was looking and NSFW and the ratio in the tub on tablet....jerking at a time in the morning I was in bed masturbating because I'm tired of waiting to have sex. Not only was he jerking when I'm available ALL THE TIME -(we both work from home), but it wasn't just porn (which to me is looking more at the act), he was looking at women who post nudes and more.... he's looking at another woman's body and masturbating instead of me. That hurts so increadibly and is devastating to my self esteem. And in case anyone is wondering, I'm a fit personal trainer who is quite pretty with an hour glass figure. This type of behaviour erodes our self esteem, our sex life, and eventually the marriage. Men don't understand how deeply women feel.
I came accidentally on this blogger who is a divorced man, that get's it. All marriage relationship stuff, and how women communicate and feel - he gets. Got it too late for himself and ended with divorce and now he blogs hoping someone out there can benefit from his mistakes. This one blog he has is in particular to this topic of masturbation and porn and neglecting of the wife in this area. Read it. Send it to your husband. I did to mine. He got the message. He appologized and said he didn't think how it would affect me - he just assumed that we watch porn together that this was ok. He was treating me how a man would react, not how I would react. Now he understand me. This guys blog is brilliant and hits the nail on the head on how most women (not all because everyone is different) want/need to be treated to feel secure, loved, and supported in the marriage.
You also need to get to a sex therepist or marriage counsellor. We are because we both realize that we, together, are worth a happy marriage. Good luck.