The Pill - What to do

I'm an athlete and never used any form of birth control. I'm 19, almost 20 and would like to try to see if it regulates my period and to be safe during sex. My period is extremely irregular, I'll skip 5-6 months without it. The gynecologist told me it's from running and I don't have enough fat on my body. I would like to try going on the pill for one month to see how it effects my running, time in the gym and my period. But my mom is convinced the pill can cause cancer. I understand her concern to an extent but now a days everything apparently causes cancer. How do I get her to just agree on me taking it for a month to try it?