If you feel like your candida is getting worse from the kefir after a long period like 2 months it could be that you need to first detox a little and clear out your colon. When you have a lot of bad gut flora, the intestines can become very acidic and when you ingest kefir it could cause too much of a "war" in your colon (good bacteria fighting the bad stuff). So, the kefir could irritate your system if it is not first prepared through a cleansing period. Try taking out the main forms of Sugar from your diet for 1-2 weeks like fruits, grains, dairy to first decrease the overall bacterial population and starve the candida. Then give kefir another try.
I dont promote kefir starter cultures (I think homemade is the best), but this site gives you an idea of how introducing Kefir can be tricky for some people.