I do want you to have an answer so I don't want you to wait anymore.
A dog’s gestational period (pregnancy) is approximately 63 days from breeding. If you actually saw your dog mate with another dog and achieve a tie(stuck together) then the odds are she is pregnant. A tie can last as little as 5 minutes but usually the tie lasts closer to 15 minutes. Now after 21 days or so, pregnancy can be confirmed by your vet with an ultrasound. Blood tests can be run to determine pregnancy after about a month pregnant. Closer to the end of pregnancy an x-ray can determine pregnancy. Without going to the vet, you might notice a mucousy clear o whitish discharge as the end of the pregnancy. During the last week of pregnancy you should be able to feel the puppies rolling inside and kicking though you have to position your hand between the rib cage and her thigh above the belly area. That is the most likely place you will feel the pups movement.
Since there might be a chance she is pregnant let me give you information on labor then I'll discuss false pregnancy and other issues that might be pertinent so you can make an informed decision based on what you are seeing.
There are three stages to labor. During the first stage the cervix dilates and contractions begin. Your female will be uncomfortable, restless, pace and pant. This lasts 6-18 hours. During the second part of labor, your female's contractions begin in ernest. Her water breaks and puppies are delivered usually after 10-30 minutes of pushing. All puppies are born during this stage.
The third stage of labor is after all pups have been delivered and is when a dog still has small contractions to expell fluids and/or placentas from the uterus. You can read more about this here:
One way of knowing when your dog with have her puppies is to take her temperature twice daily at the same time each day as her due date gets close. Keep a record of this. A dog’s normal temperature is between 101-102.5F degrees. Her temperature may rise and fall during this time, but once her temperature falls below 99 degrees, she should go into labor in the next 24 hours. The temperature drop is due to a reduction in serum progesterone levels and signals that the dog will start labor within 24 hours. You can read about this at:
You may also notice her breasts swelling during this last week of pregnancy and some milk leakage. Dogs will usually become restless and increase their digging and nesting behavior during the last week. You will notice an increase in her panting as well as a mucous discharge. You may also notice some abdominal contractions or rippling as her time grows closer. Do not be surprised if your dog is very restless and vomits as few times during this last week. Once your dog's temperature has dropped, please do not leave her alone in case of complications. As she enters actual labor you should be able to see her contractions and most dogs will begin looking at their hindquarters. An increase of licking of the genitals is normal before and during labor. Be sure and have an emergency Vet’s phone number readily available just in case of an emergency during the birthing of the puppies. Here is an excellent site about whelping.
Some other signs that my dogs always seem to exhibit are lack of appetite, frequent urination and frequent small, runny bowel movements in the day before labor starts. Frequently my dogs will start looking at their rears when the first real contractions start.
Now dogs who have not been bred will often have a little weight gain, breast development and milk production. They may adopt a toy or stuffed animals as babies. This is more common than you would think. This behavior generally only lasts a few weeks before your girl will go back to normal. A vet can help by administering medications that would help dry up the milk. Limiting water to only one cup per 8 pounds of body weight will help as well.
Now the previous expert mentioned pyometra. It is a uterine infection. Pyometra generally occurs 60-70 days after a heat cycle. It is usually seen in older unspayed females but can be seen in any age. It is diagnosed by ultrasound showing fluid in the uterus. There are two types of Pyometra (open and closed cervix) Symptoms of open cervix Pyometra are a vaginal discharge that may be pus or bloody, lethargy, anorexia, increased thirst and urination, vomiting and diarrhea, and abdominal swelling though the dog remains fairly healthy due to the infection draining from the body. Closed cervix Pyometra symptoms are the same without much of a discharge, they appear very ill, there is usually weight loss and abdominal swelling and is much more extreme. Dehydration, shock and death can occur if not treated aggressively.
So I hope I have given you enough information to determine if she is pregnant, going through a false pregnancy or something different. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.