[This is normal puppy behaviour. It is how he would have played in the litter intially although at 13 weeks you need to work hard to prevent the playbiting from now on. Please don't hold the puppy down, many trainers have told me that this has led to puppies and dogs becoming fearful and therefore turning in to aggressive dogs. Have you booked in to training classes? Understanding dogs can be a minefield and there is so much conflicting opinion. But I think some pointers in positive training methods will give you the confidence to understand your puppy more and know how to deal with this. There are some great books which others have recommended on this site. Search through all the puppy posts and you will see some excellent advice to other people who have felt like you. Honestly, I remember going through the same with our first cocker, he nearly went back. But training classes helped me understand this was entirely normal, and with our new puppy (now 9 months) I have only used ignoring, time out, and reward (treats and praise) based encouragement. Just the same as I have with my children. I know how my son would react if I held him down. I used to put myself between the child and the puppy, we yelped when he bit too hard and ignored him or put him in to time out when he got overexcited. They often overstep the mark, and it is a good idea to learn when the play is getting over excited and time to calm down required. My son is 10, and to begin with I always supervised the play closely to make sure both played appropriately. Sorry about the ramble, probably makes no sense, in a rush. Hope things improve, they grow up so fast (well as grown up as a cocker can get)
