You met three days ago? And you are “basically living together”?

Considering the length, it’s a fling. Considering you haven’t talked about it, it’s a situationship.

My unwanted and unasked advice is to take some distance for at least a day before calling it anything at all. And then talk about expectations.

Honestly (anecdote time!), when I started going out with my partner, I had some weird and totally personal hang ups with the word “boyfriend”. So for a couple of months they were “the person I am seeing” then became my “partner”. We had the conversation about exclusivity and such, talked about where we saw stuff going and so on, but wording was difficult. A word is just a word, as long as you both agree on the rest it doesn’t really matter much.