what do i do when i 18F found out my 19M fiancé cheated but won’t admit that it was him sending the messages?

yes we are young, but you know when you know and both families approve of our decision.

me and my fiancé had been together for two years and engaged for now two months.(engaged feb 10) To me we are madly in love with each other, when we’re together nothing else in the world matters, he is everything to me.

my fiancé has always been guarded of his phone, and i’ve respected his want for some privacy in some aspects of his life and never made it a point to use his phone. until recently. yesterday after getting off of work i set my phone down to change out of my work clothes, went back to grab it and it was gone from the bed. i looked for it but couldn’t find it anywhere. so i asked for his phone so i could call it to find it. he was playing the game so i was going to call it myself, not to bother him. he then told me no not to use his phone and to just keep looking for it. i asked why and he said “it probably just fell on the floor and to just keep looking” i said okay, dropped it and just finished searching. but him being weird about his phone didn’t stop, he wouldn’t let me put in on the charger like i’ve always done for him when about to go to bed, didn’t want our phones to be on my side of the bed(where the charger usually are, bc that’s the closest plug to our bed) instead put it on the desk, unplugged. now this might sound like small things im making a big deal out of but that’s been our routine for a year now and it strange for him to just change out of no where.

that’s where i made a plan( a dumb one) when i get up for work in the morning he’s still past out sleeping so i made that the time i was going to look through his phone. i did just that too. i looked through his phone and found several flirty messages to girls on instagram and fb messenger. i woke him up confronting him and he had nothing to say other than that it wasn’t him, that he shared insta with someone at the time of the messages (march 9, 24 and two days after we got engaged) and part of me wants to believe him because this is the man i want to marry but another part of me cant forget about it and just wants to talk but he won’t. he just wants to forget about it bc he says “he doesn’t want to lose me over something i didn’t do” i have no idea on how to move forward, all i want to do is cry but it’s like i feel nothing.