I don't know much about antibiotics, but it could be antibiotics as they lower the levels of good bacteria in the body which, I suppose, could cause a secondary infection... but I thought generally that was related to BM's.
Garlic is a natural antibacterial/antiviral herb (echinacea and elderberry are natural antivirals). Specialists generally recommend anywhere from 2-20 cloves a day (a huge range, I know, but it depends on your needs). For general infection, such as bladder) I would recommend taking 1-2 medium sized cloves at night to avoid smelling like garlic - your coworkers will appreciate it... your husband may not ;).
Also, cut WAY BACK on sugar, dairy, and caffeine. Sugar (predominantly speaking of refined beet and cane sugars) feeds bladder infections and lowers your immune system's ability to fight infection, as do dairy products (due to the chemicals and hormones in diary products). Caffeine is an irritant and causes inflammation (also good advice for those with inflammatory conditions/ailments).
Load up on your fresh fruits and veggies! :) They boost the immune system and will help fight infection.
Also, you might try sitting in a warm (not hot) epsom salts bath. This can improve bladder infections too.
I hope that helps... if all else fails, pay a doctor and get a different antibiotic.