Random dick pics in phone, but not sent to me

So let’s just start with this. I trust him, and we’ve never had problems before, plus he treats me like an absolute queen. And I will honestly say its hard to love me sometimes, so props to him. Anyway, he’s been acting a little different? We’ve never fought before like we’ve started to now. Idk how to explain it. Also we just had sex and he went soft pretty much halfway through. And sometimes Ik that can happen to a guy, but it really messed my head up, like is there something wrong with me? Cuz it’s happened a few times before, on and off. I’ve gone through his phone once, and this was in the beginning of the relationship and I saw he sent nasty and rude dms to girls on insta, and I’ve never seen him to be that kind of guy. But he’s always treated me respectfully and I made him apologize to the girls, cuz they were really freaked out. Anyway that’s beside the point. He was showing me a cute video of our dog on his phone when I clicked out of it, thinking nothing of it. Only to find a handful of dick pics taken over a period of time that have never been sent to me. That was the first time I’ve ever seen them. And it really threw me off. Take in mind, my last relationship I found out he was cheating on me basically the whole time. So instantly my mind wandered to the worst. I asked him why he took them, and if he sent them to anyone. And he was like no babe, I tried sending them to you, but they failed on snap.... I mean I’m trying to believe him since he’s never given me a reason not to. But idk... I need advice? Lol

Ps. I’m on my period rn so I am also a little more emotional so idk if that’s why I’m so upset too. But ya.