Do Inflammation And Itchiness In Vaginal Area Suggest STIs?

Recently I have been seeing this guy. I am on depo provera so I trusted he didn t have any STI s when we had sex. A week later I started getting itchy down there. I thought it was just a yeast infection so I just used canasten external cream. It didn t work. I kept having sex with him and it jut got itchier. It s to the point now where I can t sleep. It s red and inflamed. I did have spotting but I thought it was just from my birth control shot. Do I have vaginitis or Trichomoniasis?