I understand your feelings and your fears. Feelings for not wanting to hurt him because you care for him and fears because it’s very human to be scared with the unknown ahead.

You, guys, are still very young. Do you picture yourself falling in love with someone else? Or simply living alone?
My apologise if you already told it but I can’t recall it at this moment, do you brought out the topic with him? It’s very important he knows.

I never had more than my SO as a loving relationships so I can’t be of much help, either. Hope someone else can give you more insight.