I am sorry to hear you are worried about Bella.
You are correct, usually puppies come every 30 to 45 minutes, once labor begins.
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It is possible she is done, and she is only having 2 puppies.
The movement you feel could be her uterus contracting down, after the last pup is delivered.
The only way to know for sure if there are any more puppies would be an Xray.
Very rarely, a bitch will have one or two pups, go out of labor, and then have more as long as 24 hours later.
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If she is eating and drinking and relaxed, she does not sound like she is in danger.
Check her gums; they should be a normal bright pink color.
She may be done.
You really can't distinguish by feeling her abdomen movements of her intestines from normal post whelping uterine contractions from another puppy, or at least I can't!
You could put on a sterile glove and feel for a puppy in the birth canal, but she would probably not act so relaxed if a puppy was in the birth canal.
I have seen dogs really huge only have 1 puppy!
So I would monitor her for any signs of stress or contractions. If nothing happens by tomorrow, you could have an Xray to be sure there are no more puppies.
If she eats, if her gums are pink, she is not in distress.
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I will be checking back to see how she is tomorrow.
Continue to compare it to her sister.
But if her gums are as pink as her sister, she is probably OK.
But that could be an early sign of stress, if her tongue is pale.
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I will check back; hope to hear good news.
I would take her temperature if you can. Shivering could be from the cold, and then she should stop in a few moments. But shivering, like a pale tongue, could be an early sign of distress.
Normal rectal temp right now should be 99 to 101F.