Change in behaviour

I have a 7month old staffy. I have noticed in the last couple of weeks his nipping has gotten to be more often and more painful again. We got to a point where Joey rarely bit anyone it was mainly when he was really exited or sometimes on a night when he would have mad half hour but it did not hurt. We always discouraged it and he was getting better, but lately he keeps grabbing hold of my clothes and will not let go when i tell him to drop, he was doing really well with this. Sometimes when i go to stroke him he goes to nip and he keeps jumping up at my kids faces and although he does not leave any marks or draw blood when hes playing it has started to hurt a bit more and it really scares the kids. I know hes not being aggressive at all, but i dont understand the change in behaviour, we were doing so well.
He also tries playing with my partner on a night and will not stop when told, he gets rougher and rougher so we end up putting him in timeout, but as soon as he comes back in he starts again.
He has two hour walks a day plus playtime.

He's probably hitting his teenage stage, go back to basics and you'll get back to how you were. This may help too  

http://staffy-bull-terrier.com/stop_your_staffy_puppy_biting