I don't think these are dire warning signs. If he were pulling away from the relationship or even being supper romantic, I might be suspicious, but he's nesting! Planning for a life together with you and kids doesn't seem like a man whose cheating. He may be starting to trust in the relationship and feel comfortable to open up more to you. All of that super tough military guy stuff is how he learned to be, but he is showing you his softer side. He's being vulnerable, so be really careful at this point not to give any negative feed-back, such as accusing him of cheating because of it.
I'm assuming from your reaction to his new behavior that this was not how he acted the last time he cheated.
I'm not saying to let your guard down, I'm just saying don't jump to conclusions. If his behavior starts to get stranger or anything, then couples therapy might be in order, but until then, enjoy his new attitude.