Being introduced by name instead of Girlfriend

I'm currently 8 months pregnant. Me and my BF have been together for 4 years. He's always introduced me by name to his friends (or girls) that we run into in public instead of his girlfriend. Recently one of my friends pointed it out and makes me feel really bad that he does not introduce me as his Girlfriend. I don't know if it's the hormones or me finally seeing the truth but it bothers me now. Also, there's no pictures of us on his social media... Granted he's never on there, I just feel stupid. Is there a way to talk to him about it without sounding crazy or have I been stupid these past 4 years.