I get yeast infections a lot, though not as bad as before. There is a lot of things that can contribute to them.
First of all, whenever you go on antibiotics you really need a prescription vaginal cream that is a wide spectrum (kills a lot of various infections) and must use it the entire time you are on antibiotics, plus a few days after. Also eat yogurt. The reason is because antibiotics not only kill the bad bacteria but also the good bacteria in your intestines, etc. and your flora is off balance. You need to bring it back.
Unfortunately once you have a yeast infection you seem to become prone to them, so a few rules to follow. Cut back on sugars. Hard, but sugar feeds yeast. Same goes with fruit juices, sodas and anything sugary. Use only cotton underwear and don't use pantishields on a regular basis. If you use them during periods for tampon protection or during treating a yeast infection, change several times a day. It holds in moisture. Shower after you exercise or sweat. Moisture feeds yeast. If you are overweight that will feed the yeast. If you take bubblebaths with any scented product or use scented feminine sprays, or antibacterial or scented soaps down there, that will set off another yeast infection. Just water and basic soap like Basis or Ivory. Dry yourself extremely well. Air yourself out before putting that underwear on. Okay, maybe TMI, but it is true! Put the underwear on last! Always, always wipe from front to back. Microscopic fecal can create another yeast infection, not to mention UTI's which are dangerous when not treated quickly. Don't hang out in a wet bathing suit. Put on dry, fresh undies before going to bed. You may go through more undies, but you will have less infections. Hormonal changes throughout the month also contribute. Pay attention to when you get them and see if they come just before, during or right after your period.
My GYN is right about another thing. These 1 day or 3 day fixes are not enough. They make the symptoms ease up a bit, but before you know it, they are back. They do not do a good job of killing a yeast infection off. You need to go a full 7 days and do not skip a day. I hope this helps someone!