He treats me like a lover but says we're just friends

We usually have fun hanging out and I feel so comfortable and happy by his side. We stick to each other like glue, like an ideal couple that people often admire. It’s 6 or 7 years since it started, and we’ve met each other’s parents. Other couples in our position would have been thinking about marriage. But for us, it's different.

He doesn't consider me his girlfriend. He introduces me as a close sister to everyone even though we do things as a couple. Sometimes he texts other girls, but their conversation doesn't last long. He’s been like that since the beginning.

I'm broken-hearted, but what am I to question him? I don't know if I should stay in this relationship. Except for the fact that I'm not his girlfriend, we’re still a good fit and have lots of fun together.

Let me know your views on this.