Porn/masturbating ???

Snell
My bf watches porn about 4-5 times a week when I am not around. It isn't like we are not having sex. To much information: but we have sex 5-6 times a week. I just don't understand why he has to watch porn. I don't understand if I am doing something wrong in bed? I don't understand why he needs to watch so much porn? Is it normal for men to masturbate so much?  Why do men need to masturbate so much, when they are getting plenty of sex. I hope someone can help me
​Understand these issues before I think there is something wrong with our relationship. Thanks for your help and advice.