What do i do to get rid of a serious rash/raw skin on my vagina and butt?

Possible intertrigo: This is likely intertrigo, a heat type rash in skin folds. First, keep the area dry by blow drying after a shower and liberal powdering. Then, try 1% Hydrocortisone cream 2-3/day, and if that doesn't help, try any over the counter anti-fungal cream. Balneol is also good for this type thing. Btw, it is not your vagina, but your vulva that is involved.