Have Been Told I Have Vaginal Bacterial Infections Going On

Have been told I have vaginal bacterial infections going on instead of urinary infection. I heard if you put a tampon in yogurt and put it in you that it would help with this and when I take the tampon out I am seeing tinges of blood on it with brown blood also. Is this irritation or possible cancer going on here. Doctor thinks I need to take some estrogen cream but is this a symptom of lack of estrogen or cancer?