My boyfriends, best friend who is a girl, am I just a replacement now that she moved?

So this guy I am talking to has a girl best friend. I understand they may be just friends, but I’m afraid he doesn’t actually like me, and is using me as a medium for his emotions he might have for her. He shows me affection, made plans with me, and supports me at my events. But, I’m just afraid I’ll get hurt because he might actually not like me, I’m just afraid he likes her. She followed me on social media, probably because he told her about me. But still, I’m worried he is just sad and misses her (she’s in another state) and is using me as a way to cope with his emotions. What should I do? Should I not worry about if he likes his best friend? Should I end the relationship here? Help, thanks