My dog went into heat back at the end of April disappeared for a couple of days and returned in May, when she returned the following week she began pooping and peeing more than usual. She used to stay inside unsupervised and was able to control herself but was unable to. At this time I changed her food from regular Nutro to Nutro lamb and rice and just contributed the problem to that. When I changed it back the problem seemed to go away. She lost weight, and now roughly 6 weeks later she is larger in weight, her nipples are bigger and she eats less at each meal. Still eats the same each say just smaller amounts throughout the day.
Is it common for a dog to go through in a pregnancy? I realize I may have overlooked something else, but if you can answer without judgement I would appreciate it.

If she is gaining weight and showing signs of getting ready to produce milk she probably is pregnant. The eating could be mornin g sickness or she is carrying a lot of pups meaning she has less room for food in her stomach, so keep food available for her to eat at all times smaller amounts. She could have had a bladder infection or a dog STD causing the previous incontinence/frequency. You should have kept her in or spayed her really because you have no idea what sort of dog she was running around with, the pups gerenally take after their father and she could be having pups that are too large for her to safely deliver, or she could have contracted an infection that could endanger the pups at birth. like a herpes infection.

Hikingmomof3... I know I am going to pee you off and maybe some more around here.

Take your dog to the nearest pound or rescue if you can't be a better owner than what you have demonstrated so far.

I can understand that sometimes people do not have the funds to spay their dog right away or you could have just gotten her.

I can even understand maybe her running away and getting pregnant.

But my goodness it has been since April and you have yet to take her to a vet to see what is going on and you have banished her to live outside because you fail to take care of her properly. It is untelling what type of illness she contracted from the other dog that she needs treatment for. Get your head out of your rear end and read up on humane treatment of animals and get your dog the help she needs and deserves.
What the hell is wrong with you...

Well, I knew posting a question of this nature would get such a response since you don't know me or how my dog is actually kept I will ignore the comment.
However, the problem did not last long it did stop after I changed her food, she was on nutro lamb and rice, she was on nutro before she ran away and after just I changed it lamb and rice, don't know if it was food that maybe she was allergic to or a symptom of pregnancy, should have included that before.
Also don't judge just answer if you can. This is summary of the situation and you don't have all the history of the dog or family, don't make it out to be more than it is.

Get your dog to a vet. Being pregnant I would think she should be eating more not less. Maybe she is eating less due to the heat.

Also you need to have her on puppy chow.

Even though your post ticked me off... kudos to you for even responding back and trying to get even this much help for her.
You really need to get some books on the birthing process and taking care of puppies, socializing etc... If you'll check back in I will post what I can.
*edit* heat as in weather

Articles (http://www.woodhavenlabs.com/articles.html)

Also you may find some help in this thread

https://www.askmehelpdesk.com/dogs/whelping-puppies-urgent-151659.html?highlight=pregnant+pitbull

It's not normal for a pregnant dog to loose bowel or bladder control. (She may have been involved in a scuffle between rival males and could have injured her back.)
It is normal for them to eat smaller more frequent meals in late pregnancy because there is less room for the stomach to distend, but an increased demand for calories.
I would take her to the vet to confirm that she is pregnant, x-rayed to determine size and number of puppies and that her pelvis has not been broken (which usually reduces the size of the birth canal)
There are some sexually transmitted canine diseases. One of them, Brucellosis, can be transmitted to humans by contact with the birth fluids.
Once this litter is on the ground, plan to have her spayed so her hormones don't get the best of her next time, or one of her boyfriends doesn't decide to come courting her at home!

Lamb and rice is the diet you would feed an animal that has allergies or diarrhea. As far as I know there is no allergy to lamb or rice documented