my bitch is so gentle when getting in her box and cleaning them but when it comes to laying down she just sits on them as they all horde to one corner where the heat pad is and she wants to be there some can get out but others get stuck and im terrified of her squashing them she isnt particularly heavy 13kg but to them she will be

At this stage you pretty much need to be there 24/7 to hike her off and rescue them, as bitches can and do crush pups, it is one of the common causes of neonatal death. 

Does the whelping box have  pig rail?

I always have the heat pad in the middle that Way the bitch can lie around the edges and the pups tend to be in the middle and less likely to get crushed into the sides of the box, though of course she can still flop onto them.

hi it has pigrails but no matter where i put the heat pad she wants to be on it even though she is getting rather hot

Ashleigh

I have found that the best way to deal with this is everytime mum moves scooping the puppies to one side and then keeping my arms around them until she has settled again.  When they became more wriggly I put them in a box (although I only had 8 not the 13 you have) and retruned them one by one once mum was sorted.  I sleep by the whelping box for the first week so that I can quickly sort out any problems as they arise.  The first few days I actually have my arm on mum to reassure her and also feel when she moves.

how about getting another heat pad???

just a thought, not sure how practical it would be ....

why not try a heat lamp rather than pad?