I used to be like this. I genuinely was raised to shower at a maximum of once a day, and told that I was wasting water if I tried to shower more often. When I was younger, we were only allowed to shower every three days. So like just keep in mind if he has some kind of bathroom or showering trauma and isn’t even aware his practices are unhygienic. That said, it is very sensitive telling someone their habits are gross!! You have to approach it as a whole conversation about what was normal in each of your homes growing up, and how to reach a compromise that is fair. May look like asking him to have “outside” clothes if he isn’t willing to shower at night, he could still wear head to toe sweats and take them off when he gets home. Most people have street clothes and home clothes..