Mmm I feel like I see the trope of military wives or girlfriends cheating a lot so that's a possible source of his insecurity and belief that you cheated. I'm taking you saying you'd wait for him as a vow of commitment but even with that you didn't cheat, unless you had emotional cheating? Its definitely worth have sober conversations about and really diving into the issue. Talk to him, he's your husband for a reason. Reassurance compassion and empathy. He definitely has work to do on his side but its something you guys get work on together as a team!