Quoting Ashley Yarber:" Almost all, if not all, men masturbate. My boyfriend is a man. This is kinda obvious. It bothers me, ... [snip!] ... the day. I feel like he has two sex lives. One, with himself. And ours, which is steadily decreasing. It's so upsetting. :/"
In my house porn is a big no no for religious and non religious reasons.
Masturbation is ok as long as we are masturbating about only eachother.
Ofcourse if it became something that he became obsessed with and he did it more then we had sex, that would be an issue.
Try and join in on it if you know he's doing it maybe go and "help" him. haha.
About the shower thing when you were in there with him, I might be a bit weirded out honestly and I'd talk to him about atleast letting me know before he goes and does that.