He never asked me out..

(Long but questions at the end!) So I went to high school with my current SO but we never became friends until my second semester of college. We had a class together where we got along very well, strictly as friends as I was well aware of the girl he was dating who also graduated from the same high school.

Fast forward to the end of summer, they had been broken up for a few months and he invited me over. We were never in contact since the last day of our class together, but he had my number from a group project we did together.

He lives with a mutual friend who eventually convinced me to come over, and I immediately hit it off with my (now) SO. I ended up spending the night that night...and the next night and the next night and almost every night since then ! We were together almost all the time, and while we did have a few minor arguments, everything has been great.

It's been about 5 months now of basically living with him. He never flat out asked me to be his girlfriend, but it's understood at this point and he does call me his gf now. We haven't said we love each other yet, but I'm literally having to bite my tongue!

Everything is amazing right now, but is it possible it could just be the "honeymoon" stage? Since he never technically asked me out, what would be our anniversary?