This is my third month using Nuvaring and now I feel that my body has adjusted. My first month, I followed the instructions and inserted it on Day 1 of my cycle. Similiar to another post (cslayton) I bleed the entire first three weeks I had it in. My off week was a very light light spotting -- we're talking pink water. Month 2 was fine. My off week (2nd) was finally normal. I took it out and three days later started my period. My period was finally enough to justify using a tampon and it only lasted three THREE days! Yay!
The only side effects I've noticed is that on the day I take it out (in the am) I get a massive migraine about 8 hours later but if I take a 1/2 hour nap it subsides. Also, on the day I insert a new ring (in the am) about 8 hours later I am extremely exhausted and take a two to three hour nap. This is bothersome only from the fact that my day is a Tuesday -- work day.
I have hypothroidism and was briefly concerned with the fatigue but realized that it is only on the days I take the hormones out and put them back in. I haven't noticed any other listed side effects or at least haven't connected the dots yet. It is VERY TRUE that the ring either works for you or it doesn't.