Need help being sneaky and stealing boyfriends phone to check he's not cheating?

[Sam]

Basically I need help devising a plan to take his phone. I know he talks to girls via twitter, snapchat, messaging obviously..he's cheated three times in the past by arranging things through technology. I need to know whether it's fourth time (un)lucky, and I had my suspicions which have been confirmed earlier today - I went on to his phone, saw direct messages from about 7 or 8 girls and conversations looked flirty and cheeky..went onto his old phone and saw he was texting girls I don't even know about and an anonymous number saying they loved him..so I need help devising a plan in which to actually take his phone from him, sneakily and unknowingly, because I need to thoroughly see the conversations as I only had about 10 seconds of seeing them today.
Any help would be appreciated.

So need a plan to steal his phone..ins and outs please!

Also if you know a way to find out his passwords? I know I sound like a psycho but I need to know!

[TeamSheeran]

It's not right to invade his personal things, even if you are suspicious, confront him directly and be the bigger person.
What's a relationship without trust?

[OllieVee]

You already know!!! What's the point!!!
Why not just take him on Jeremy Kyle and make him take a lie detector test, really show yourself up!! Have some respect for yourself for gods sake and tell the cheating arse hole it's over!

Unless you like the drama???? Stop being so bloody weak and move on!!!

[Margaret A]

i have another 'plan' for you. you don't trust him so leave him. simple.