We "officially" got engaged a week ago.

We've only been together for 6 months.

Since then, I realized that maybe this isn't a good idea

I would be less worried about there being a spark and more worried that you think getting engaged at the 6 month mark to a 24 yr old that you barely know isn't the red flag you should be concerned about. Please do hold off on wedding planning.

If there is no spark, why did you get engaged? If you are unsure how to have a healthy relationship, wouldn't it be prudent to work on recognizing healthy and unhealthy dynamics within a relationship vs. (apparently) believing that whatever relationship you are in is THE relationship? It is called dating for a reason. You date, you figure out what you're looking for in a partner, what is totally unacceptable, what your goals are, what your relationship goals are, etc.