not sure if this helps
I personally have something called polycystic ovary disease. I causes very irregular periods, makes it very difficult to get pregnant and increase rate of miscarrage. It also can cause a higher level of birth defects. It is very difficult to diagnose and i spent 5yrs before i had a dr to the proper hormonal testing to figure it out. there are other symptoms as well.( can gain weight easily,pelvic pain,can be prone to diabetes but not all women have them) It sounds to me like she may have a hormone imbalance. I can't see why a dog couldn't have this same disease. also there is no "cure" just managing symptoms. see if the vet can check to see if her "male" hormone(androgens) levels are 2 high.