***In my humble opinion, I think the first and third sentences would complement each other nicely, if combined into the same paragraph at the beginning of the story, and the wording smoothed out just a tad for good flow and imagery. For example: in line one you have
"It is sixty-two days into Belle's pregnancy. She has been doing great and putting on the weight." Then in the third sentence you have
"She is beautiful and watching her waddle around the house is just too funny. She loves having her big belly rubbed often."
What if you were to combine them something like this?
"It is sixty-two days into Belle's pregnancy. She's been progressing great and her weight gain is right on target. It's been a riot watching as she waddles around the house and seeing that cute round belly exposed, when she rolls over, requesting a much loved tummy rub.
Again, this is only a suggestion, along with an example of what I am thinking might work a little better for you.
***In this sentence:
"She is a Tri-colored ~ Shih-Tzu, with lots of brown long flowing hair, mixed with white and black tips at her ears." You could make it flow more smoothly by showing, more than telling. For example:
The beautiful tri-colored Shih-Tzu sports a flowing, silk-like, brown coat, ears tipped with black and white accents. (we already know it is a "she" by the previous sentence, so no need to state it again here.) But do you see how just a few changes in how it is worded paints more of a picture in the readers mind? That is what you are after in your writing. That is what grabs and hooks the reader and keeps them devouring your story. They like to feel like they are right there in it, 'seeing it' themselves. (then move on to the 4th line, where you are speaking to her.
***Here, in the dialogue of the fourth line:
"Come here mama Belle, come let me brush your pretty hair and tail," I said", maybe consider
"Come here mama Belle, come let me brush you, pretty girl." (This tells us you will be brushing her hair and tail, yet smooths it out and simplifies it for the reader. No need to get over detailed on what you are trying to express, as it can become tedious for the reader.}
***Then here,
"So I brush the hair in front of her face and grabbed up a bunch of Belle's hair at the top of her head and pulled it up tight, then with a hair band I begin creating a 'doggie hairdo.'" Consider not drawing out the actions quite as much. Perhaps something like
"After the gentle smoothing of her hair (fur?), I gather a large section from her head, pulling it up snuggly into a creative 'doggie updo', complete with a pink satin bow." Remember, these are only suggestions. I am not trying to re-write your story, just help you find ways to more creatively word it through examples.
So these above suggestions are some examples on the smoothing out and the "show don't tell" It also has helped to eliminate over use the the same word, such as she or her. So I would like to suggest that as you go back through your story, watch for those types of overuses, and find a way around it by changing sentence structure or combining short paragraphs that go well together into a slightly longer, single paragraph.
***In this sentence,
"I look fat, that's it, I am a fat little dog!" It appears she does not like having a huge belly. It is obvious you are sharing what you feel the dog is thinking. Thoughts are usually notated in creative writing by using italics, not parenthesis.
***This sentence would be great, if you made a change to give more of a visual:
"The unborn puppies are due any time now, her belly is swollen like a balloon with too much air in it and at a closer look, the baby's are moving." The unborn pups are due any time, her belly is swollen like an overinflated balloon. Upon closer inspection, I notice they are squirming within her, as if confirming the fact." Or something like that.
*** Next, just try to pick out the couple of small things I noticed that were not in the present tense, like the majority of the story is.
One such place is here: "Nathan asks me if he
could can help do something?" This also is a sentence, not a question, so no question mark needed, just a comma.
***So now, my final suggestion is to watch your spacing and keep it consistent. Single spaced paragraphs and double spaces between each paragraph.