REALLY EMBARRASSING Acne on butt?

Umm, this is sort of creepy to ask about, but it's really starting to bug me. When I was really little (like 8 or so) I was at the party at my aunt's work place. They had a dunk tank, bouncy house, and all sorts of outdoor things, but it was raining. I was in shorts and had developed a rash on my vagina and butt the next morning. I went to the doctor and they told me what to do. It went away but a year or so later these bumps came back and have been coming and going for the past few years. It's really bugging me. Also (super embarrassing), I found this bump on my vagina a few days ago, guessing it was another pimple or whatever. But its actually too big to be a pimple or acne. I tried popping it, but it won't go away. My parents don't know about any of this recent stuff, and I'm too embarrassed!

{Edited by RealSelf: link removed, did not link to pertinent information}