Anybody help?

so for maybe a year now, I've been getting this bumpy, red, rash looking thing, and it always has a sort of wet feel to it down where my bikini line is, and I have no clue what it is, it can be there for anything up to 2 weeks, and then vanish. and it hurts like hell, even showering, when the water touches it, it's like a burning/stinging sensation. but as soon as it's gone, it's back again, and I don't really have anyone I can speak to about this. I know it's a vague description, but is there anyone that possibly knows anything?