I just googled this song. If you add one word in between I'm and yours it will help. The word is "completely". If you look at what he said right before I'm yours: "But I won't hesitate no more, no more, it cannot wait-- I'm yours"
I think he saying he's not going to waste any more time pretending or withholding anything. He's now completely giving himself to her/surrendering. "I'm yours"