Wtf... my boyfriend told me he calls another girl "boo". Is this a deal breaker?

I had exactly the same problem my boyfriend use to call another girl beautiful and i didn't feel special anymore i felt like that he didn't mean it when he said it to me. I thought im his girlfriend and only i should be called that. When i told him he kept saying that im making a big deal but i thought it was a big deal. Don't worry you are special and you deserve someone to give you all the attention and only have sweet names for you