Making me sick 😷

I've been taking the same type of bc for almost a year, and every few months the symptoms change, the past few months has been some pretty bad nausea, should I change my bc or should I wait it out and hope it stops?? Also, if I change the brand of pill I take, how long do I wait till it takes effect? Or does it work right away if I don't stop the pills I'm currently on?