Cheating

What's the best way to find out if someone is cheating other than going through phones? I respect privacy (kind of) but mainly wouldn't because I already tried that and don't know his password and feel like he'd be smart enough to delete stuff. He's not sneaky but pretty private. We used to stay out late ALL the time together, then he wanted to just do his own thing which is cool except the staying out late thing as we get older it's just an annoying habit for me personally. Another thing is anytime I walk by I feel like he'll put his phone down. It's not necessarily always face down but it just feels like he's on high edge about something. Any tips on how to find out if my inuition is right? We also don't use condoms but I got some free once from PP and we saved em and they were just in his sock drawer. Months/year later he threw those away but kept some condoms (also old) that are more flavored or the fire/ice kind -granted they aren't new but I just thought it was weird to keep a certain kind when we don't use em at all anyway. I know it probably sounds like I'm being paranoid but I also don't wanna brush things off and end up getting played in the end. Any tips/feedback I greatly appreciate (even if ya wanna tell me I need to calm down 😅)