I am 20 years old, and my girlfriend and me have been sexually active for 3 years. I have only been with her sexually, but these past few days I have been feeling very itchy on the inside of my vagina. I never thought a female could give another female an std, but I am really starting to wonder. She has cheated on me twice, so there is a possibility that she could have contracted an std from somewhere else. Can two women give each other STDs?