Fiancé acting STRANGE

Mattie • Married & a happy nurse 👩‍⚕️❤️
So I've been seeing my man for three years now, we know everything about each other and I definitely love him. We just got engaged three months ago, and our wedding is next summer. But he's been acting strange; I.e. Going out late, hiding his phone (mainly his Snapchat), partying with people I don't know, all kinds of bullshit. And then when I bring something up, I'm awful and nagging and acting like a crazy lady. Am I in the wrong here or does it actually seem like something's up? It's not that I don't trust him, but his behavior has just been too weird lately to not be a little scared. I don't wanna lose him 😩 we've been trough so much, because he's in the Army and just got home from deployment. I worry that I'm not enough for him.