will birth control make me gain weight??

I'm 17 and just starting the patch this Sunday. I've already picked up my prescription, and I'm excited. But I was reading more into it online and now I'm not so sure if I should be on it. It says it's less affective (92% affective) for women over 200 pounds. I weight about 230. I'm also already a heavier girl, and I've heard I could gain anywhere from 10-30 pounds. And if that's the case I most definitely cannot be on birth control.