Im scared to go on birth control

I'm only 14 but i have horrible periods and symptoms, they are to the point where I sometimes pass out because of my cramps. I'm scheduled to see an gynecologist (for the first time) on Monday, but my mom says she thinks he might put me on birth control to even my hormones out or to help my period become less painful and heavy. But again I'm only 14 and I've read about the long term effects of birth control (like trouble getting pregnant when I'm older) and it scares me.