Blake Shelton, 44, just can’t believe Gwen Stefani, 51, is going to be his bride. “Blake has always been in disbelief that Gwen is with him,” a source tells HollywoodLife EXCLUSIVELY. “He’s always joked but also meant it that she is way out of his league and he can’t believe she’s chosen to be with him. They have a really health and happy relationship and truly love one another,” the insider added of the oh-so-in-love couple.