Hi so a bit of background first,
I met my partner 2 years ago whilst at work. I was single he was in a non-committed relationship. We got together things moved pretty fast. Fast forward and we have a 5 month old DS.
He’s always been hugely possessive. I’ve had to change email, phone number and he’s blocked a lot of people from my Instagram. I’ve had to delete facebook and snapchat. If I do much as glance in the direction of another man I get accusations of me fancying him and I want him. He wanted me to cut of my best friend and this caused endless rows. I don’t return his behaviour. If he wants to go out with friends I encourage it, I want him to see I trust him so he should trust me, I literally say stay safe and have fun. He keeps his phone hidden a lot and takes it to the toilet all the time. I didn’t think much of it, usually I hear him watching videos on performance cars and know he sometimes uses going to the toilet as a bit of an escape. I don’t got through his phone. I know his unlock code but not any passwords and have honestly never felt the need to snoop.
So a few days ago it was late and DS was asleep. I was googling something on his phone from my phone IYSWIM. So I had both phones in my hand. As I’m googling he receives a message on Instagram from a girl whose name I don’t recognise. The message said “it’s not that bad”. He looked a bit sheepish and said he didn’t know her. I still had the phone in my hand at this point so I replied “whats not that bad?” I said if it’s just a random then she’ll reply accordingly. I clicked on her profile and they both follow each other. I asked about this and he just parroted the same line about not knowing her and it must’ve been a random add. At this point he declares he needs the toilet (despite going only about 10 minutes before). He snatches the phone from my hands and takes it to the toilet. He comes back 10 minutes later and I asked if there was a reply. He says “yeh she said it was a mistake and I deleted the messages.” Why would he delete the messages if it proved it wasn’t anything. I also asked him this and he said he just did it without thinking.
So I thought this was a bit fishy. I asked him to block her on Instagram as she might be trying it on and I didn’t trust her. (Yes I know I sound as bad as him now but I wanted to see his reaction). He pulled a face and said he was sick of being interrogated about to and she didn’t need blocking. I pushed it again and he did it in a huff. Although he did ask if he could just unfollow rather than block. I asked him to block and he got pissed off about. Anyway the next day I ask if he’s got her on Facebook. He said no but I had to ask him to speak up as he was mumbling. Almost like if he ever got caught he could deny saying no. He said no clearly and promised me and again I got the whole Guilt trip about not trusting him. This was in the morning. We go out and about take DS swimming, pop out around town and come home. I decided to text my best mate who said they’d see if they could find anything on Facebook as I don’t have it. (Something didn’t sit right). About 7pm on the evening he send me a screenshot of this girls Facebook. She’s change her profile picture that same day at 7am and he’s gone and liked it!
I suspect they know each other from work. His employer has asked him to do nights recently. I used to know all the other colleagues at his previous place of employment and can’t think where else he’d know her from.
I’m guessing he’s messaging her on Facebook now but I’ve no way of knowing.
So do I confront him now with what I have? He’ll deny everything and there’ll always be a sense of doubt that I was being paranoid and overreacting and threw everything away for nothing. Or do I wait to try and find more evidence? If so how? He never leaves his phone unattended. Ever. I thought about confronting him with what I had then demanding his phone and sending her a “test message” if you like from his profile.
I don’t know what to do 
. Ideally I’d like more proof but struggling with how to come up with it. He’s not the type to confess even if I push him.