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!