Is it possible for men to use condoms themselves?

No, unless he is abnormal, he can't play with condoms at home, that is, you don't have any sexual relations with him. If he wants to, he will ask you instead of using condoms at home.

But that doesn't mean he cheated. If you catch him, you can't say he cheated. Also, if he really cheated, would he be stupid enough not to throw away the condom for you to find out? Does he want to be with you? I'm sorry to say that, so I let you know that he needs you to do this.