I've been using NuvaRing for about 8 months, and I am discontinuing it for several reasons. I know what you're saying about it falling out... and that can happen more often in you have a tipped uterus (which I do, and you may have... it's not a serious condition or anything, just the way our bodies are).
My boyfriend absolutely HATES it as he says it feels very uncomfortable when we have sex. I also noticed that it would slip down when I went to the bathroom or even after working out, and I know that it was pressed all the way against my cervix when I inserted it. I just kept pushing it back, as far as it would go.
There isn't anything you can do; it's just not right for some people. My best friend also uses NuvaRing and LOVES it. I guess we're all just different! But as for me, I have an appointment tomorrow with my ObGyn to discuss other alternatives... probably the Mirena IUD (I don't want children for a long time, so this appears to be a great option).
I would suggest making a call to your doc... voice your concerns and go from there. Hope this helps!