Jamie2006,
the yeast infection could be a caused partially by your nuvaring, however is probably mainly caused from intercourse. If you are not having intercourse ( I am only assuming because you are on birth control), then it is most likely from the nuvaring. To help minimize yeast infections try to remember urinating before and after sexual intercourse. This will help minimize any chances of a uti also. I would still stay on it and if the yeast infections are reoccurring, then I would talk to your physician about another possible form of birth control.
Some women simply cannot keep the ring in, and it just isn't for them. Just try to always make sure it is pushed as far back as your body will let you. It shouldn't be slipping out during normal bowel movements, but perhaps during straining (ie constipation). Make sure you incorporate a lot of fiber into your diet which will help with the digestive processes, thus preventing any constipation.
However if you are still having problems and it can't be tolerated, then you may need to switch to another form of birth control. I was on the nuvaring about a year and did indeed like it the best because of the low amount of hormones when compared to other types. I since then have been off of hormones all together simply because my body cannot tolerate them. Hope this helped. Best of luck!
Natalie