Help!!

So my boyfriends has this friend who is getting married in March, and in February they are having a Wedding Shower. Well my SO was invited and wants me to go. Well I don't know anyone who's going to be there BUT my SO and the Groom. Well I'm not a very social person when it comes to things like this. If I'm not in a big group of people that I know I feel comfortable with than I won't come out of my bubble. And I told my SO this and he got mad because he went to New Orleans with me and my baby sister to a One Direction concert, so I feel like should go because he did that, but I rly don't want to... what should I do????