You need to try to eradicate the problem out in your yard. Basically his potty area is probably where he picked them up.
There are sprays you can get to remove the fleas from the area.
Or, a natural flea preventative is diatomaceous earth. You can spread the non food grade type all over outside to get rid of the problem now. They even recommend spreading inside then leave sit for a bit before vacuuming to get the fleas that are probably already in the house out. Check local feed stores as a possible place to buy it, or do an online search.
And you can feed the food grade DE to your bully to keep fleas off. (It's got other benefits too) we fed it to HRH this summer instead of other flea products and never had a problem. We purchased it at Carolina Pet Pantry.