There is a condition in female dogs and cats known as "ovarian remnant
syndrome" in which a spayed female continues to exhibit signs of estrus
(heat periods. Usually this occurs because a portion of an ovary was left
in the abdomen during the spay surgery. This can happen several ways --
sometimes the surgeon doesn't have a clear view of the ovary for some
reason (obesity, not having a big enough incision, bleeding, etc.) and a
portion is simply missed, other times it is a piece of the ovary is
accidentally dropped as it is removed and reimplants in the abdomen. I have
had a couple of patients in our practice that appeared to have small pieces
of ovary near the normal ovarian tissue but separate from it. So far we
have seen these pieces and removed them but I tend to think that there are
times when there is just extra ovarian tissue. Dogs that have ovarian
tissue that is not removed during a spay tend to show all the normal signs
of heat -- swelling of the vulva, bleeding, attraction of male dogs and
often false pregnancy signs. These usually occur at the same interval as
other estrus periods, roughly seven months. Cats tend to have normal estrus
behavior for their species, too. This can be crying, rolling on the floor,
overly friendly behavior and attraction of male cats at about 3 week
intervals. The only treatment I know of is to find the ovarian tissue that
remains and to remove it. This is easiest to do when the pet is in estrus
because the ovarian tissue is active and easier to find.

In a dog that has already had exploratory surgery once I think it would be
a good idea to do hormonal testing prior to considering another surgery.
Sometimes it is possible to tell that ovarian tissue remains just by
testing progesterone levels in dogs but only if the progesterone levels are
over 2ng/ml. A hormonal response test that starts with administration of
HCG (human chorionic gonadotropin) during estrus behavior and then is
followed by measurement of progesterone is more accurate.

Source: http://www.vetinfo.com/dfemale.html#False%20heat

---

Hope this helps and if I've answered your question don't forget to please accept my answer and to make it twice as nice a bonus (no matter the size) is always appreciated!

Thanks,
Rebekah

There is such a thing known as 'stump pyometra' which is an infection of the remains left behind when a female is spayed.
This can happen if a bit of uterine horn was left behind or if the dog is an XXY instead of an XX in genetic make up.
If she is going through false pregnancy etc I would expect a hormonal disruption from either undetected ovarian material or perhaps a pituitary problem.
You might want to seek out a vet who specializes in reproduction in dogs to get some ideas on how to handle this.
Hope this helps!

---

Please press Accept if you find my answer helpful. Want more info? Just reply on your question!
Bonuses for good work are always appreciated!
Thanks for the opportunity to help you!