What Is The Swelling In My Labia After Masturbating?

Hi, I am 23, since past few weeks when I masturbate , i noticed that my labia majora swells, I am a virgin, never had seX with anyone.I get it when I masturbate and it goes away after a day or sometimes half day. It sometimes hurts badly during masturbation too. recently I also have something like a rash on both sides of my labia, maybe its an allergic reaction from the hair removing creme but I don't know :( Is it possible to get STD of diseases like this just by masturbating? PLEASE HELP ME :(