My DH and I have been invited to the wedding of his friend. DH accepted on our behalf and I had initially been really looking forward to it. It's a church wedding in the summer, and I think it will be a lovely day.
Although I know the friend well - I don't know much about his fiancée except for the fact that she is a very devout person - CoE I think? The friend is not. I am also an atheist, but I am mostly indifferent to religion - each to their own.
So here's my problem - past experience has told me that, during v. religious ceremonies I do tend to start internally giggling/silent laughing quite uncontrollably - particularly when it's clear that no laughing is allowed.
I don't do it on purpose, and I do my best to control it - but I have just realised that this wedding ceremony will be a bit of a danger zone for me - particularly because the ceremony is quite long, and we've heard through the grapevine that we've been invited "to a wedding, not a party." 
I just feel so out of place, and I can't get into singing the songs/saying the prayers at all. It just feels very silly to me - I don't believe a word of it. And my shoulders start shaking like crazy while I try to control it - and of course that sets my DH off too!
AIBU to just not go? My DH will be quite disappointed, we've already spent quite a bit of money on it, and the friend is looking forward to us coming. But I don't want to spoil it for anyone!