I'm in the same boat as you, only I'm on the opposite end. I'm 21 and my boyfriend is 38. I had a wee bit of problem with the age thing at the outset but like everyone else has so wisely said 'If you're happy, then screw all the rest.' The more you allow this to bother you, the more problems it's going to create in your relationship and why would you want to mess up a perfectly good thing just because you are a little older?
And if it makes you feel any better, 12 years is not as bas as 18 years
I say congrats to you for finding someone who makes you happy! Enjoy it!