Doubling up on birth control will not reduce the risk of pregnancy. Taking too much birth control can cause weight gain, depression, dryness of the eyes, blood clots, high blood pressure, and headache.
Don't do it. One pill will work well enough. The amount of hormones can mess with your body and cause your period to be lost for while or even make it come early.
If you are using non-hormonal methods, such as a condom and an IUD, or male condom and female condom, there is no risk. The only risk is if you double up on hormonal birth control, such as two kinds of birth control pills at once.
I take birth control. Sometimes I miss a day. I always double up on it. If i miss Fridays pill I will take it on Saturday with Saturdays pills. Sometimes it upsets my stomach if i havent eaten. Other then that its fine!
First, doubling up on your birth control won't protect you better. The only reason to take two at once is if you missed a dose. But it should never get to be a habit. If you find that you keep forgetting you should come up with a way to remind yourself.