I suffer from OCD too, so I can relate with what your going through.
I saw Pirates of the Caribbean a little a while ago, and if it makes you feel any better, your not missing out on much. The whole movie all I could think about is how dirty everything in the movie was. It made me really nervous, and I didn't enjoy it. It does suck seeing how you loose out on the free movie ticket, but if it causes extra stress, then even if it's free it's not worth it.
It doesn't matter if you can sing well or not, as long as you can sing, and you have fun doing it thats all that matters. I'm sure you have a beautiful voice.

Jen.