How to know if your so is cheating?

Honestly his phone is always in his pocket and I ask him to keep it out because I find it weird it’s never around and he takes it everywhere. I don’t see this as controlling, I would understand cause we’re married and if you have nothing to hide it won’t be a problem.

However every time I ask he never listens and says “he’s not going to cater and feed my insecurity” so he still keeps it away. Every bathroom trip, (which I do too) but when Itsleft out to be seen when I’m around him.

There have been other instances lately but the main issue is how do I get his phone !! I don’t want to ask him cause “I always have a problem” but we have a baby and I’m currently pregnant so I really want to make sure I’m not being played.

He charges it at night and it’s there but if I move I know he’ll wake up. 😖 please don’t judge me, it’s not as simple as just asking him cause he doesn’t see anything wrong with this.