I want to marry my girlfriend but don't want to upset my son

I am a 44-year-old man, with a seven-year-old son. His mother and I are divorced, and I moved out when he was three. We share custody; he is with me three days/ nights a week. He is a very happy child and the most precious thing to me.

- Annalisa Barbieri

I have been in a steady relationship with a remarkable woman for three years. She and my son get along beautifully; he looks forward to seeing her and she loves him very much.

I've been considering remarrying, but I am worried it might have an adverse effect on my son.

While he has spent loads of time with my girlfriend and me, it seems he has yet to grasp that we are in a relationship. A few months ago, he heard me refer to her as “my girlfriend” and said: “I thought she was a friend. I didn’t know she was your girlfriend.” We didn’t discuss it further and I took care to never refer to her as “my girlfriend”.

I don’t know how to speak to him about it without making him insecure or confused. But I also feel it might be better to take this step now than later, when he is a preteen/teen. I don’t know if I am being overcautious, but I don’t want to do anything that interferes with his childhood and happiness.