Is My Dog a Pit Bull?

I was hoping to get some opinions as to whether or not my puppy is a pure bred or mix breed Pit Bull. We got him from ladies who said they rescued dogs in their area and found them homes. They had a female from another litter that was mixed. They also had this male they said was pure bred. They claimed to have seen the parents and had no reason to lie because I would have taken either dog. They said the age was around 3 to 4 months.