My 12 year old daughter has been experiencing vaginal fishy odor discharge itchy and frequent urination i took her to the pediatrician but there was no infection.so is it hormones,toxins in her body or puberty because she started her period at 10?

Odor & discharge at that age suggest a minor vaginal infection by common bacteria, not a UTI. The inner surfaces of her vagina make a mucus that can support bacterial growth. Random self contamination does occur. If the ped did not do a wet prep exam/culture of the discharge they would not find the cause. You might contact your OBGYN & ask their guidance.