I used to get bladder infections a lot when I was younger. I was told it was allergies to certain soaps. Do you take bubble baths? If so, stop taking them. How old are you? Have you asked your doctor why you keep getting them? If not, perhaps start there.
GIRLSRULE1 said EXACTLY what I was going to. Girls do not realize how dangerous it is to wipe the wrong way (sorry guys) And, yes many soaps can contribute to them. You can now buy a large of variety of cleansing products that are very mild yet very effective. And, as usual, Cj is correct. My daughter's Dr. told her not to take bubble baths any more than once a week....as this contributes also. On an additional note, if your doctor did not already warn you, be careful while on all of these antibiotics. Many antibiotics also cause yeast infections. Ask your pharmacist when you get the antibiotic, as some cause them more than others. I always eat yogurt when I take antibiotics just in case.
I don't know if you are male or female, or how old you are, but I will tell you that my doc told me to always empty my bladder after having sex. Drinking cranberry juice changes the pH of your urine and helps prevent bladder infections. Drink plenty of water.
Wear cotton underwear and pants that are not spandex or polyester. If you've been really hot or active, change your underwear. That whole area needs to breathe. Shower every day. Using baby wash products might work better. They smell nice, are gentle, and are inexpensive.