I have a 22 week male staffy and he wee's constantly and he doesn't even have to of had something to drink eirther

It sounds like he might have a bladder infection, a UTI. Please take him to the vet. You don't want this getting worse and affecting his kidneys.

How long has this been happening?

There are only two reasons for this, medical or behavioral. As soon as all medical issues are ruled, out you can narrow it down to certain behavioral issues, such as separation anxiety or dominance. Are there other pets in the home, how long have you had the pup for? Is he up to date with de-wormer and flea treatments? Where did you get your pup from? The more detail the better chances of us getting down to the bottom of things. Where does he do his urinating, does he seem to know what he is doing (does he stop to squat or does he just urinate while sleeping?)?