Tim McGraw believes if it weren't for his wife, Faith HIll, he might not be alive today.

"Faith has kept me alive," Tim tells PEOPLE. "She's saved my life in a lot of different ways -- from myself more than anything. She's loved me through times when I didn't love me. I can go down a dark road sometimes, when you're not feeling good about yourself -- and she pulls me out."

Happily married to Faith for 13 years and the father of three daughters, Gracie, 12, Maggie, 11, and Audrey, 7, Tim says bluntly that if it weren't for his wife, "I'd be dead. Oh yeah, I would have partied too hard. I might have caught myself somewhere along the way and put the brakes on. I don't know if I would have gone [to rehab]; don't think I could have been talked into that during those times."

And nothing has put the brakes on for the singer quite like being dad to three girls fast approaching their teen years. "I'm probably more the disciplinarian. I do try to be tough, not mean, just firm. You have to be; it's just scary with girls. There's so much that could go wrong. But they're really good kids."

Tim also reveals that three is enough when it comes to kids, even though they'd always envisioned adding a few more to the roost. "We talked about it once. We even have names for boys. I would love to have a boy also, but if we start again now, we're going to be old when they're gone. We started out wanting five [kids], and life just ... got busy."

In addition to dad detail, Tim's staying busy these days with his just-released 'Southern Voice' album. And later this month, he'll be seen along with Sandra Bullock in the feature film, 'The Blind Side.'