Its 4 weeks today since the last mating, should i be seeing some sort of signs by now, she's a small breed she's sleeping a lot more than usual , her nipples look slightly pinker and larger than normal but thats about it

Still to early to tell, although it depends on how well you know your own dog sometimes. Not even half way yet & equivelent to 4 months in a human....Give another week/10 days  & it may be easier...although pugs are cobby bodied so it wouldnt be as easy as my breed to see.

Her lady bits are still quite swollen as well, whereas usually it goes back to normal size, ..i hate the waiting :(

> Her lady bits are still quite swollen as well, whereas usually it goes back to normal size, .

This tended to be what gave me confidence that there was a pregnancy going on.   Sometimes a bitch will be more careful of themselves, not rough-housing with the others as before.   I'd maybe see a bit of thickening of the flanks by 4 -5  weeks, but having a breed with a 'well sprung' ribcage, not much else.   I didn't bother with scans but by around 7 weeks, the puppies could be seen moving around.  Again unless it was just a small litter with them still being carried well up under the ribs.