My boyfriend takes his phone into the bathroom everytime he goes to the bathroom, should I be suspicious of this?

It's not when he pees, it's when he goes to take a dump lol. He takes his phone EVERY time and I'm worried if he's hiding something. When I ask him why he says because he likes to look up stuff, like cars for sale on Craigslist, articles, etc, while taking a dump. He's in there for a long time too. It's not a short time. He keeps his phone on him like no other, very rarely he'll leave his phone alone with me in the room. He will say to me "here go through it. There's nothing in there." I refuse to do that. And it doesn't help anyways because he could have deleted the message from girls and what not. One time I did a wrong thing by looking through his phone while he was sleeping and I found nothing suspicious at all. However he did suspicious things in the past, so that's why I'm kinda insecure because he did cheat on me in the past. We were only broken up for a day and he was talking to girls and shacked up with one in a hotel. I still consider that cheating. He said he learned from that and will never do it again but it created trust issues. So I wanted others opinions on this. Should I be worried? Is he possibly cheating? Or is it a guy thing to take their phone while taking a dump to look up stuff? Like I said he tells me to go through his phone but I refuse to.
My boyfriend takes his phone into the bathroom everytime he goes to the bathroom, should I be suspicious of this?
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