My fiancé m25 went through my phone f21 while I was sleeping and is now treating me like crap over something from before we met

TL;DR:
My fiancé went through my phone while I was asleep, downloaded all my Snapchat and Facebook data, and is now acting cold and jealous over a guy I had a fling with before I even knew he existed. He’s trying to match up dates and make it seem shady, but it had nothing to do with him. I feel hurt, trapped, and alone. He had a gf now btw as he’s stalked him!

Last night while I was asleep, my fiancé went through my phone and downloaded all my Snapchat and Facebook data. I woke up and saw this random Snapchat file — thought I’d misclicked, but he admitted he did it.

Then he starts asking why I blocked some guy on a certain date. That guy was someone I had a small fling with before I even knew my fiancé existed. But now he’s acting jealous and controlling, trying to work out when I spoke to that guy, when we blocked each other, everything. Like I even remember.

Now he’s being cold, ignoring me, and treating me like I’ve done something wrong — over something that had nothing to do with him. It’s honestly messed up. Just two days ago we were painting rocks together, now he’s completely switched. I didn’t even know you could download all that data, so he must’ve looked up how to do it. I feel hurt and alone, and I don’t think I can deal with this anymore.

I had a 3year long relationship
Then the fling for a few months I wasn’t into him so we ended it slept together one time!! I’m open and honest.

My fiancé was a virgin before me.