I don't get it, am I missing something lol

So girl's I always here about us going thru our man's phone but never him doing it to us. Well I found my man going thur mine last night. I don't get it I haven't gave him a reason to think something bad so why? He tried to play it off too lol like my phone was going off and he just checked it but he was lying? I was just like ok so let me see ur phone then and he had some guys number save under the auto parts store idk I didn't even know how to react at first, like is he looking for a reason to be break up and thought I was talking to someone or something was on my phone that shouldn't be? What do y'all think? I'm not sure what to do?