I agree that your BF should have introduced you around the table. When he didn't do so, the host(s) should have introduced themselves and said "Welcome." A question, Were you invited personally? No matter what, his aunt should have been a gracious host, but if your BF didn't ask if you could come, it might have been wierd for her. (my younger bro is famous for this, every new GF [one very few months or so, so far, with a few long-term GFs thrown in] is the love of his life, and has to come to every family activity at his insistence.)
Something similar happened when I met my ex-BF's extended family, so I finally just said, "Hi, everyone, I'm so-and-so".
BTW, the bringing a dessert was a VERY classy move.
It's too bad his family didn't make you feel more comfortable, though.