Constipated or labor ???

I haven’t been going very often so my dr told me take miralax every 4 hours. So today I took it 3 times throughout the day. I just woke up out of a dead sleep feeling like I’m gonna throw up and bad stomach pain. So I’ve been puking a little and just feel nauseous. I still haven’t gone poop. Could this be labor or I’m just extremely constipated ??