He introduced me as his Lady Friend?

I’m pissed but actually hurt . I’ve been with this man for a little over a year. We got our own place together 7 months ago and I am now pregnant with his child (13 weeks 4 days). Tonight his brother came over to visit and to introduce us to his new girlfriend. His brother starts off “Hey guys, this is so and so my girl.” We say hi and my man introduces himself then me as “This is Bri, my lady friend.” I looked at him and said “Your lady friend?” He stops then says “Yea I guess I should say baby mama now.” His brother interrupts and says “Don’t call her that, if you want to say the mother of your unborn child that’s one thing.” I didn’t say shit after that. I’ve been thinking about it all night. I feel like he tried to downplay the role I play in his life. And with all the wife material shit I do for this man it really fucked me up I don’t even get the title of your girlfriend? Then you call me your baby mama? I don’t know maybe it’s pregnancy hormones but this upset me and I can’t quit thinking about it. Any advice? Talking to him about it isn’t the answer he’s just say I’m trying to fight. Am I wrong to be upset?