Is it worth breaking up over?

My boyfriend recently ( the 11th of February kind of recently) texted his ex that she's "the one that got away" 😔 Not sure how to feel about this. its the first time he's ever done something like this but is it enough to end the relationship? I just feel disrespected by the entire situation.
Thoughts?
N.B. He has been my boyfriend for 4 months now not since the 11th of February.