A 17 year old with vulvar cancer? Please help.?

How common is this? I'm 17 years old and I think I have found a lump in my right labia majora. It has a red ball type part and attached to it is an irregularly shaped elongated mass. It runs lengthwise toward my backside, and it's somewhat hard. I first noticed it over a year ago and mentioned it to my family doctor, but she told me it was nothing to worry about (very rare). I think it's gotten bigger, but I don't know if that's just in my head. I've been researching it online, and this one website (a href="http://www.canceranswers.com/Vulvar.Cancer.html)" rel="nofollow"http://www.canceranswers.com/Vulvar.Canc…/a says that backpain is common. My back has really been bothering me lately, but I also have a slight scoliosis. Again, I don't know if this is all in my head or if I should be scared. What am I supposed to do? I'm scared. Please help me.