I'm not sure if it's even possible for the string to break based on how it was installed. The only reason I can think of is that it was installed on a loose tuning peg, which it wasn't (I made sure to slightly tighten the extra-loose ones).

I'm a beginner guitar player, so the other issue that I can think of is that I'm playing incorrectly. The song I've been learning after re-stringing my guitar is "Layla" by Eric Clapton, which involves a lot of bending. I'm sure it contributed, but one week shouldn't be enough to break the string, right?

And I should mention that they are cheap strings: they're called "Ernie Ball" strings. However, I think they are the same kind that were already on the guitar when I got it about six months ago, and I haven't had to re-string the guitar until this one time (when the D string broke a few weeks ago).

Is this common? If not, what are some issues I should watch out for?

Thanks for taking a look!