Is it a red flag to talk about the possibility of a break up in a relationship?

So im in a long distance relationship and my boyfriend talked about the possibility of us breaking up one day in the future. Just a possibility really. The future is so uncertain. And the time it would take to close the distance thats also a factor too.

I reacted pretty badly too this 'possibility' of a break up. I just felt so hurt that he could even think like this when im just unable to even think of it :((

Am i over reacting?
Is it a red flag to talk about the possibility of a break up in a relationship?
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