Sorry to hear that your pup isn't doing so well. It sounds like it could be a UTI, if it is they will most likely give you antibiotics for it. I don't really think that the yelping could be because of teething. They usually chew on things to sooth teething pains.
Don't worry I don't think she'll go in to heat right away, and even if she doesn't don't fret about the breast cancer thing, its never a 'for sure' thing.
Please keep us updated.