Without pictures it's hard to tell. There are a few dog breeds that have the Pitbull look to them. The two I know of are the Pitbull and the American Staffordshire Terrier. The American Staffordshire terrier is a relative of the Pitbull. The one American Staffordshire Terrier I came across, I mistook him for a Pitbull, was really sweet and loving. All he wanted was attention.
Here's more information on the breed. American Staffordshire Terrier Information and Pictures
It's not the end of the world if he is a cross with a Pitbull though, you'll just have to keep a closer eye on him. Or he could just have a different facial structure. You won't know until you test for his breeding.