What Could A Painless, Round Growth On My Vagina That Leaks Fluid Indicate?

Some time ago I noticed a different skin on my vagina which was mildly attached to my vagina.I didn t feel pain when I pressed it, so I didn t pay much attention to it again.But when I saw today that same skin has now grown up, at once it is round like a small ball and when I pressed it, water came out from inside it.Today is the 2nd day of my period: and now I am getting very tense, is this not a disease, isn t it?