NuvaRing - side effects or?

For the past week, I've been having some moderate nausea on and off. I've been taking zofran for it since it gets overwhelming and even caused me to leave work early last week. However, I haven't experienced nausea this long with nuvaring before. The only time I recall nausea with it is the very first day I started using it. Since then, it's been fine. I've also had some very slight, bright pink bleeding after sex. Are these symptoms due to nuvaring or something else?

My period is supposed to start this coming Sunday or Monday. I'm on week 3 and take the ring out this Friday. I was a little paranoid about pregnancy but I've taken about 3 tests and they've all been negative. I know it could be too early to tell, though.

Is it more likely to be nuvaring side effects or should I be worried about something else? Has anyone else experienced this?