Christina Aguilera is officially off the market. The pop songstress is engaged to longtime boyfriend Matthew Rutler, the producer whom she has been with since the end of 2010. Her beau popped the question on Valentine's Day during a romantic day together, and she broke the news on Twitter with a photo of their clasped hands and her huge diamond sparkler. "He asked and I said . . ." she captioned the photo. Congratulations to the happy couple, and check out Christina's ring below!