I know the answer as to how they decide what to give you as I work in a lab.....they test for sensitivities against a few of the main antibiotics and go with what shows as most effective, or something from the same antibiotic family. Each infection can be sensitive to differing antibiotics each time, not always the same ones. Plus there is antibiotic prescribing guidelines set out for each board/trust. We restrict ones which are not as effective or can cause other more serious side effects, even ones which are just too costly to treat simple infections.
Hope you ladies start to feel better soon-eating whilst wanting to throw up is no fun and it is just a horrible circle! Good luck.
Xxxx