I know you must be going through hell right now, but I have a story that might make you think somethings just "happen".
We had a female Yorkie mix several years ago. She found us. And she was pregnant. Ok, so she had her puppies---3 of them, all completely different from the others! Took her to the vet after the pups were weaned. He spayed her, but he too could only find one of her ovaries!
So, life went on. She came back in heat after about 6 months. She got bred by the neighbors dog. Completely by accident!! And no puppies!! This happened for quite a long time. She'd come in, just like normal, breed with whoever she chose and not have to worry about the after effects. She had a ball!! And she was always sooo proud of herself after she got bred!
