With the natural yoghurt, it's probably best to insert it yourself. Make sure it's the natural yoghurt though.
You can also try drinking cranberry juice, or a teaspoon of bi-carb soda in a glass of water. These 2 methods will lower the ph in your urine.
If it keeps recurring, best to get it checked out by your GP. Also the suggestion about getting your DP checked out is a good one too, otherwise it'll be going backwards and forwards between you both.