Question about my dog?

I need to know what kind of dog I have. I've had him since he was a puppy ( he's 5 now). I know he is Black Lab. At first my aunt told me he was inbred. I don't think so because he is an incredibly smart dog. But, a while ago, when she telling someone about him, she said his dad was the pit bull from next door (and not his brother). I never noticed but, he does look like he may be Lab/ Pit mix. He is basically a Black Lab, but short and stocky, and he has like a big alligator head. And he has a white patch shaped kind of like a W on his chest. Whenever he fights with our Rhodesian Ridgeback, he totally owns him (he alsmost broke his leg about a year ago). I might be able to put a pic up within the next few days. Any guesses with just the info would be appreciated.