I don't take Seasonique, I take regular birth control pills (Ovcon) and skip the placebo week. I haven't had a period in around 3 years. When I do, it's maybe once a year. No side effects - I may have had some break through bleeding when I first started. I honestly can't remember.
It's worked great for me! My Gyno told me I can keep taking them up until I start menopause and intend to do just that.

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There are so many colors in the rainbow
So many colors in the morning sun
So many colors in the flower and I see every one!
-Harry Chapin