There will be a ton of other things happening that you can do during freshers' week, I promise. I mean, apart from anything else your question here is basically 'will I miss out by not doing the thing where I'm unable to communicate and in massive physical discomfort' and honestly, not doing that doesn't sound like missing out to me! But, you'll have the chance to go along to other, more chilled-out events (which actually, some of your new flatmates may be interested in doing that and want to come along, too) so you don't have to just sit at home. What usually happens in freshers' week is, people meet and hang out for an evening, but then never actually see those people again and instead make friends over time with people from their flat/course/societies/sports teams. You aren't missing some fundamental thing. You may feel a bit out-of-everything to begin with, but actually that's normal and most people feel that way sometimes even if they go out every night.