Getting rid of social gathering anxiety!

My boyfriend really wants me to attend his family's Easter get together. The only problem is I'm a nervous wreck when I'm around tons of people all at once. We have been together for over a year, live together and I have yet to comfortably attend one of his family's events. I went last Easter but didn't speak, wouldn't let him out of arms reach and we ended up leaving early because of me. I've avoided all his family's holidays since. But I know he really wants me to come to this one and I really would like to go. It would mean a whole lot to him but I just can't get the right mindset to go and enjoy it! I have really bad anxiety and things like this make it 10x worse but I really want to do this for him. Please help! Give me some tips on how to get through it.