Multi-year drug user here of whatever was available.
I thought the same thing. It didn't affect my ability to be with my friends, loved ones, workmates, the world.
I used a little here and a little there to get me through the day. I used it like a carrot for the end of the day. One day I needed that little burst to get me started in the morning and push me off into the world. It was the beginning of the end. It started with a little, then a little took a lot, which seemed like just a little, but it really was a lot.
I hid it from friends and from loved ones for the most part. Some knew. Others had no idea.
My advice, seek guidance in
Ala-non. It may seem hokey and stupid. But find shelter there in understanding what is going on around you.
As far as your SO is concerned. He will not stop until he decides it is time to stop. It may be tomorrow. It may be years. It isn't yours to decide, you only can decide what you do for your life and your life alone.
good luck.