Be sneaky, find trust, insecurities, HELP.

So my boyfriend of 5 years is extremely protective over his phone like to the point where I can even hold his phone and he will be like “Babe stop before you piss me off” and will come run and get it or even tackle me for it playfully..but will try that hard to get it from me. The other day he got it from me and ran and locked himself in the bathroom claiming he didn’t delete anything but then came out and threw his phone at me letting me go through it.. AFTER he locked himself in the bathroom?? Hmm don’t seem right. Though we we’re messing around I took it really seriously and now I’m not feeling secure as a girlfriend right now..If he catches me trying to go through his phone the day is done for cause there isn’t turning back after that cause he will be pissed at me all day. He claims it’s cause he doesn’t like that I don’t trust him and feel the need to look through his phone but honestly him being so protective is what’s creating my trust issue.. I completely trusted him until a few days ago when this all started up again.. so my question is.. should I sneak onto his phone while he’s sleeping? I’m so bad at being sneaky I know I’ll get caught and I’m so scarred of being caught by him cause it won’t end well... but I feel like I have no other choice to set my mind at ease.. all I can think about is what’s on that phone?! It makes me not even want to lay with him cause I get in my head so much.. What would you girls do...?

If you’re wondering about other girls:

There are two other girls that I know he talks to that I never really had a problem with cause I trusted him.. one girl is from his work but he has a boyfriend. Last time I went through his phone he was texting her being super playful and she was buying him stuff before work and he invited her and I think her boyfriend to go bowling with us and all our friends without me even knowing that idea but she couldn’t come and he acted sad and said maybe another weekend. But for one I’m a super jealous girl lol so I would never want her to go bowling with us that’s weird. Just not me. But he claims they’re just good friends whatever.

Another girl is one of our super close friends in our friend group who’s married, all of us go to her house all the time and have little get togethers and play games but he’s just too caring around her I guess?? We all know our boyfriends and know how they get.. but they are best friends on Snapchat, they message each other all the time, we had a get together at her house once and I walked in the kitchen and it was just them two sitting on the floor talking, it was just weird but he claims she just wanted to talk about things that were bothering her about her husband... They just seem too close for comfort to me and I know it’s nothing, I know it’s in my head I trust her, I just don’t trust his feelings.

So now that I’m insecure as shit, I’m always bitchy, never having a good time while we’re out cause I can never get out of my head, always irritated or annoyed while he has a great time with our friends but all I can focus on is how he’s being with that girl. Never wanting to be intimate cause what if he is messing around on me? I just need reassurance.. and he closes up whenever I want to talk about it cause he thinks I don’t trust him and it pisses him off..

How do I gain that trust back, and help my insecurities...