SOCIAL MEDIA TROUBLE

Today my boyfriend went through my phone and is accusing me of some sort of cheating with this student from 3 years ago (just an FYI me and my bf are barely 10 months into our relationship).. my boyfriend and i agreed to delete all of our social media because a similar situation occured but on his end during our 3 months. We did not want that to jeopardize our relationship and that’s what I THOUGHT was happening... but A few months later i find out that he has SC and didnt want to tell me until it was convenient for him, so I let it slide... but I was so deep into my thoughts that I was questioning if he was really all in for us. Now, THIS happened and i am the one to blame for old SC messages with a student from 3 years ago who had a major crush on me... is this backfire or did he bring this upon himself?