<human>: So today I met up with my boyfriend to have dinner at his place. He bought me a huge bunch of roses and spent a long while preparing dinner (something he doesn't usually do). Anyway, something felt a bit strange, so I checked his phone after he fell asleep.

He'd been messaging with a friend of his from many years back. She had just broken up with her long term boyfriend. My boyfriend's reaction was to tell her that he would leave me for her. She said "what, your girlfriend of over a year?" And he said "yes, I've been thinking of breaking up with her recently because I've been treating her so badly". She replied with disbelief. 

These messages were from over a week ago. Just last week I went to a family dinner with his parents, siblings and grandparents. I can't believe that he would say things like this to someone.

My question is, should I just break up with him now, right before Valentine's Day? I asked him about whether there was anyone else and he said "no" and that he's happy with me. Either he's lying or the conversation with his friend is no longer relevant. But even if it's no longer relevant in his mind, shouldn't it be relevant to me because one's significant other shouldn't ever say that to someone else?

I'm fairly certain that he hasn't cheated on me.

Could you distill the essence of the text into 1-3 sentences?
<bot>: My boyfriend told an old friend that he would leave me for her, but now doesn't feel as though that is relevant. What should I do?