Is my dog in labor??????

She is pregnant about 60 days into her pregnancy. She has been panting since about 9:00 this morning and its now almost 3pm. She doesn't seem to terribly uncomfortable but she doesnt want to lay down. Shes panting with her mouth open and its causing her to drool a little bit. We made her a box but she doesnt seem to want to stay in it. Does this sound like shes in labor? If so how long until she starts delievering??