My mized breed dog is very pregnant and we think she is going to have her pups any day now. So what can I look for to tell if she is ready to have pups? Right now she is shaking, and breathing heavily, nad is very restless. Are these signs that she is ready? And how long can a dog be in labor? Is there any way we can help her. PLease let me know soon.

it sounds like shes starting her labour, have you given her a whelping box, she needs somewhere that she has privacy, also fill it with newspapers as they often like to tear and shred the paper up when theyre contracting, -you also need to tell your vet  you think shes started incase you need to call them out, or take her in,