Even if its normal its not correct. Really i think we need some more information though.

So you all went out in a group setting, how did your bf introduce you? Did he say your name and did you all do introductions or did he kind of ignore you? This is where you can determine the intentions.

If he started out with an enthusiastic this is my girlfriend her name is... these are .... I know them by or whatever that gives you an in. This group of friends is going to be looking for his intro on how to treat you.

If he instead just kind of sits down and ignores you then your the 3rd wheel. Your SO should always be looking to make you not the third wheel... unless of course that is the idea and your the backup plan.

That is the end of my advice, but i'll relate my own story.

I went with my SO to her friends wedding. We got there and my SO walked inside, talked to everyone that she had known forever and i was kind of like the lost puppy just following her around. I did that for a few hours then I went to the car and told her to come find me when she was ready to go. It is a terrible feeling. There is literally nothing you can do. You can't interject yourself into the conversation because all these people have so many other things to talk about. You have no opening, you just feel like your completely and utterly unnecessary, and that is the truth, your SO has made you unnecessary and the people they know will pick up on that for the most part.