The couple began dating last year and are growing strong, reported People magazine.
"They are not engaged yet. Everyone is expecting it to happen at some point, though. Gwen is very, very happy with Blake. She always acts giddy when she talks about Blake," a source said.
"There are no immediate plans for their future, but it's a serious relationship. Shelton makes efforts to stay in very close touch even when they're both traveling," the source added.
Shelton, 40, has also been very supportive of his girlfriend's career.