I have a friend who was in her 30s with braces, and an aunt in her 50s with them currently. They were/are both self-conscious about their braces.
I really don't think your boyfriend has any say in you getting dental work done. He'd have about as much say as what type of birth control - a pill v. IUD v. Implanon. When it comes down to it, it is your body and your decision. I'm married and my husband and I bounce ideas off each other, but really it boils down to what makes us individually happy.
I say go for it. It's better to do it now and get it over with than spend months or even years agonizing over the thought and being unhappy when you look in the mirror.