The British singer popped the question to dental nurse Rosanna Jasmin during a romantic getaway in Paris, France last Monday (23Dec13).
He has now revealed Jasmin is expecting the couple's first child.
He tells Britain's Sunday Mirror newspaper, "This is the best Christmas present I've ever had. I'm going to be a dad with the love of my life... I am seriously the happiest I've ever been right now."
"Me and the (Blue) boys had our album out, we've done The Big Reunion (Tv show), and we're touring. Now Rosanna and I have a baby on the way - it's like everything's falling into place."
Blue took part in U.K. Tv show The Big Reunion earlier this year (13), reuniting top pop acts from the 1990s and 2000s for a British tour.