All is time off he spends with them
He spends all his time off with condoms? Weird.
Well, you can simply ask him about it. You know, something like "hey, any reason you started keeping condoms around since we don't use them?"
His having this condom could be totally innocent. Maybe he bought some a while back and came across this one the other day and just tossed it in his drawer. You don't know and the only way to ease your mind will be to ask him. Nicely. And in a non-accusatory manner.