In the blunt words of Dan Savage, dump the motherfucker already.
I personally, doubt anyone wants to have to hide something like that from your partner, just as no man should have to be shamed over occasionally watching porn on the internet. And they certainly don't want a partner who makes that kind of value judgement on something like this.
Also, don't just "take a break while he gets better" or anything like that. I totally understand if he's going through a hard time, however, you also need to do what's good for you. It's not your job to wait around and sneak around until he can sort himself out.