My boyfriend has asked me to feature in his band's music video?

I think this is a great opportunity for you!! congratulations. This will be the best way to get over your shyness. After all it's up to you to create the person you want to be. Do you want to be utterly shy till the rest of your life? or do you wanna look back one day and say "that was me in that video and it was the first time i ever took that advanced step to do something good for myself". Stare in the video it will do you some good and shape up your personality, who knows if some promoter will see you. You might even get into the world of show biz. Of course there are possibilities that you might not do good, but you'll never know until you give it a shot, test your abilities. Besides sometimes not being good enough may appeal to others. Look at Tim Burton (a great director) he claims he was the worst artist when he was young, but it's because of those bad drawings that people love them so much. it's the bad things that make them good. Same thing may go for you. May be you mess up or you trip and fall but when the audience see's you get back up on your feet laughing like you just experienced the funniest thing they will laugh with you and support you. It's all about having fun. So do it for yourself, experience a new part of yourself, and most of all have the fun all to yourself. You'll love it. Congratulations again, i hope you realize how many people are out there fighting/auditioning to get into something like this. This is like a one time thing, to most of us i guess. Good luck.