It could be a few things. Maybe a urine infection, so get him checked at the vets first of all. It could also be that he wasn't kept in very clean conditions with his breeder and so learnt to soil his bed there. What sort of place did you buy him from? Where/ was he kept? Were you allowed to make uninvited visits?

Other than that, it is quite rare for pups to do this. I would maybe put his crate inside a puppy pen so he can have access to the pen and put a toilet area in the pen (newspaper or turf if you can, as he already knows to go on grass) Make sure the toilet area is as far as possible from his crate.

I'm not a fan of putting tolet areas in crates themselves, to be honest, especialyl if your pup is already toileting in his crate, as the two are just then too close together and it might confuse him.