Cjr has a good point about trying to self treat withough involving a practitioner in the process. It is important to know what you are treating. This is true whether you are treating with over the counter, homeopathic, or herbal supplements.
If your yeast infection is recurrent, make sure your doc/mw is taking a swab and looking at it under the microscope. Yeast is very distinct.
It is true that the ph changes of the pregnant vagina provides a more positive growth medium for yeast overgrowth. Acidophilus/probiotics, either insterted vaginally, taken orally, or both, have been proven very effective in our practice. However, they seem to work better preemptively or right at the first sign of yeasty beasties. Now, many people do not buy this; there have been a couple of studies and they are inconclusive, whether the acidophilus helped or not. BUT, oral acidophilus has been definitively shown to help prevent overgrowth of yeast in AIDs patients; so to me, that shows that oral intake does indeed affect systemic health.
Your doc has a point; if there is alot of sugar in the yogurt, that might be counter productive. Choose a plain, no sugar yogurt with a high culture count...Nancy's is always good, for one recommendation.
The garlic thing has personally worked for me. I recommend a triple whammy to my friends: mix a couple of drops of tea tree oil with 1/4 cup or so of olive oil. Soak a piece of cotton gauze or cloth in the mixture. Wrap a peeled clove of garlic in the gauze, and insert before bed. If you are having internal irritation, rub the olive and tea tree oil mixture on your vulva. Do for three nights; usually this helps me. The olive oil is particularly soothing, I find. Better than yogurt, and not so funky feeling.
A couple of months ago, however, I got a RAGING yeast infection that nothing I tried helped. I have never been so uncomfortable; I was taking 800 mg of Ibuprofen every 8 hours to deal with the discomfort. Luckily I work at a birth center....I hopped up on the table and had the mw take a swab, because it was beginning to feel like something else to me. Nope, just a hell of alot of yeast, having a party. I did a three day over the counter treatment that included a vulvular cream, and that cleared it right up. I then did the garlic/tea tree/olive oil thing for three more nights. No problems since.
If you go over the counter, I would do the three day, as opposed to the one day or the seven day. The three day has a stronger dose than the 7 day (but less than the 1 day). The one day seems to often not really take care of it, but it is too high of a dose to do several days in a row. Many of our clients who use the over the counter find that the three day is just right.
BUT, whatever you do, your doc/mw needs to know that you are treating yourself for yeast, and that you are struggling with it.
Premature rupture of membranes has been associated with recurrent vaginal infections (usually BV). Yeast is indicative of an imbalance, which also puts you are greater risk for other vaginal infections, including BV. You don't want your bag of waters to be compromised by either the recurrent infection and inflammation or the recurrent treatment.
So good luck, whatever you decide to do! Yeast is NO FUN, and if it isn't responding to treatment, you need to ascertain that it isn't something else. I hope you get some relief soon!!