Lump on labia majora?

I'm 15 years old, I'm on sertraline for anxiety & depression and suffer badly, kinda a hypochondriac too. I'm laid in bed out the blue I just touched my vagina and felt a small lump, you cant see anything there but on the labia majora on the left side is a small lump on the soft peice of skin on the outer lip area in the middle if you know what I mean? No pain and never noticed it before but I'm worried and thinking all sorts of serious things now.. as i said it's not visible and I'm still a virgin.. any ideas what this could be? Not due on my period for another 12 days btw, thanks :( x