Boyfriend problems

My boyfriend broke up with me today after this boy I went to high school texted me at 4 this morning. Something I was not entertaining nor had control over.

Anyway, so my boyfriend was very upset and looked at it as I was messing with him... when i wasn’t. A couple days ago my boyfriend and i had taken a break or whatever. Something he wanted... Monday was my birthday my friend from high school messages me on Instagram and says happy birthday I reply say thanks end of convo... the next morning after my birthday I wake up next to my boyfriend say something about him being my boyfriend and he reply’s I’m not your boyfriend then argues with me. Out of anger and hurt I vented to my friend that had texted me. My boyfriend now believes I’m lieing and was messing around with this boy when i had no intentions of doing so and the proof was in the screenshots. Am I in the wrong please hear me out . A lot of my friends say I’m not but I need others opinions who I don’t know lol .