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It really sounds like you are seeing the stages of labor, particularly since she is clingy and her temp has dropped so low. If you don't see puppies within a reasonable amount of time, you need to go ahead and give your vet a call.
You should have seen her lose her mucus plug about a week ago. This might have looked like a snotty mess that you could wipe away.
Aside from that, you might feel her sides ripple when she has contractions.
Keep in mind that pugs often need c-sections so don't wait too long before calling the vet. She may just need a shot of oxytocin to get things moving.
It definitely sounds like you can expect puppies any minute!
If you have not seen anything by tomorrow, go ahead and see your vet.