Hon, you need to get on a high quality probiotic ('friendly' bacteria) supplement (from the fridge of your local health food store). Take a capsule every morning before food and last thing before bed. Needs to be kept in fridge. This will also increase your body's absorption of nutrients - important during pregnancy.
Canesten does not treat the cause of the problem (an overgrowth of yeast or bad bacteria in the digestive tract due to insufficient probiotic bacteria) hence why it just keeps coming back.
The reason you get it during pregnancy is that rising estrogen levels can make your body more acidic and less alkaline (as does the pill), making your digestive tract a more hospitable environment for bad bacteria like yeast to flourish. Untreated, the yeast will spread to the reproductive tract in the form of thrush.
Take the probiotics, start having a serve of natural yogurt with a high probiotic count every day (Mundella is good), restrict yeasty or sugary refined foods - especially vegemite and yeasty breads and white grains. Eating a predominantly alkaline diet (wholemeal bread, pasta, rice etc and loads of fresh veg) will ensure the thrush is unlikely to return. Google alkaline diet to find out more. Taking the probiotics durinf breastfeeding will also build the immune function of the growing infant as it enters the breastmilk.

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