What Causes Itchy Red Rash On Outer Labia?

Hi I have noticed a rash on the outer labia, i noticed it because of itching and irritation. Iv just stopped menstruating 2 days ago and it s pretty much similar to a nappy rash or that s what I thought until I got a mirror and looked. It is red and lumped but the skin seems broken in parts and leaking pink watery fluid, what could this be?