Had Sex About A Week Ago & Started My Period

Had sex about a week ago & started my period right after; then on the last day of my period I felt a slight bump near my urethra put neosporin on it and woke up with a ton of red itchy bumps all on the inner vaginal lips... It's super tender to touch I don't know if it's from running too much in a thong the other day or an allergic reaction a yeast infection or an std?!!!